And saying "Just one more game before I go to sleep" or suffering through that god damned meat carnival are 100% enjoyable and not addiction in the slightest.
Or, if you would rather, "they are buying and playing some of the worst games out there for no other reason than to bolster a completely meaningless number" works perfectly for pretty much any MMO, JRPG, 4X game, or anything with stats.
Or, if you would rather, "they are buying and playing some of the worst games out there for no other reason than to see what happens to some fake character" works perfectly for every single SP game with a plot.
Seriously, people get enjoyment from different things. You would think that people who play video games would realize that not everybody enjoys the same things.

Kind of like people who get 1000/1000 in Avatar The Last Airbender, its not a good game by most accounts and it's the easiest game on record for you to get 1000 in, it can literally happen in 3-5 minutes of button mashing. I'm sure there's people who enjoy it but I'm equally sure that a larger number rented it to get a quick score boost

Are they doing it for enjoyment or purely out of compulsion? That's the question here.
Can you honestly not see a problem with people spending a ton of time and money on games they don't even enjoy playing? When all they're getting out of it is a single meaningless number?
If they were doing it for enjoyment then why not stick to games they actually might... enjoy? Why turn it into a chore by playing games they clearly have no interest in anything about save for the points they can score?
You ask why gamers can't relate to people enjoying different things. But us being gamers is exactly why we can't relate to that: we game for our enjoyment. Not to bolster a number. We do that enough in our working lives as it is. We don't need it in our gaming lives too.

One could easily argue that a lot of gamers do things out of compulsion. Again, the damned meat carnival.
And they do stick to games they enjoy: the Gamerscore Game.
They game for their enjoyment. They just don't game the way you want to.

I'm hoping that most of the copies sold were bought by the fanbase. Anyone who bought it for the points would be shooting themselves in the foot. For as soon as that game was seen in their collection any 'value' attached to the score is obliterated.

And what exactly makes you so certain of this?

I am just as certain that they game for their enjoyment as I am that we game for our own. Again, I cite that damned meat carnival as an example suggesting we might not.

Achievements are an ingeniously insidious way of keeping players interested without actually adding new content or putting in any additional effort aside from a line of coding and small graphical badge. Having previously played WoW I rarely paid attention to them unless they were in the form of a challenge doing a particular encounter. The wacky ones, the completion/collection ones I totally ignored.
As far as other games I usually shoot for them so long as they aren't particularly laborious or annoying.

So it's completely baseless assumption then. But then that wouldn't be a first.
Not everything that everyone does is for their own enjoyment. Or even has any beneficial qualities whatsoever. In fact, in case it's news to you: people can become addicted to things that are very harmful to them indeed.

Yeah, heaven forbid I don't instantly side with your baseless assumption that they are all idiotic freaks who should learn to only do the things I like to do :p
Seriously, there is plenty of room for other people to enjoy things. And what is so harmful about playing games to get a high score?
I always find it hilarious how people get offended by anyone who has a slightly different viewpoint. It is almost as though people are afraid that they are going to lessen our fun by having their own.
Or maybe it is just that I still have memories of gaming before the fratboy revolution, when gaming wasn't fully accepted and people actually tried to be somewhat tolerant of others.
Heaven forbid you ever hear about people who play tabletop warfare games. I know people who spend more on miniatures in one month than I spend on games in a year :p. They must be REAL freaks in your eyes.

While I understand perfectly that different people enjoy different things, the impression I got from the article is that this woman isn't grinding her gamerscore because she gets some kind of enjoyment out of it (although it probably started as such), but rather because it's become a matter of habit for her. While psychological addiction is a fairly nebulous concept that's often difficult to pin down, spending large amounts of time on an activity that is no longer enjoyable but more just a matter of habit is a key factor in most of the definitions of psychological addiction that are out there. Additionally, the fact that she'll unilaterally pull sizable sums of money out of her and her husband's bank account to support her activity also points to an addiction as opposed to an activity that someone is doing out of enjoyment. While I dislike playing an armchair psychologist, these are the impressions I got from reading about this woman, and it also reminds me of my own experience when I used to play Diablo 2 a lot (and I consider my experience there a case of mild psychological addiction).

Read the article in its entirety its all in there.
“I definitely play more games I don’t enjoy than games I do,” she says. “Like, maybe 65 percent of the games I play I don’t enjoy.”
“I keep saying when I get 200,000 gamerscore, I’m going to retire,” Kristen says. “There are people who do that. I say it now, but I don’t think you can ever actually quit. It’s like a drug. It is addicting.”
“It’s very much a personal pride thing, being ranked in the top five in the world in something, whether it’s gaming or the fact I’m a female gamer,” Kristen says. “I’m never going to be in the Olympics, so I’ll be a great gamer. It’s something I know I’m good at.”
I think those 3 quotes sum up fairly well what its about for her.
I was in one of the finest raiding guilds in WOW when it first launched so I can see where shes coming from. You tend to play through hours and hours of bordem for that rush of achievement and the feeling of being one of the best in the world. People get kicks out of being the best at something regardless of how pointless or boring it may seem to others. I just hope for her sake she doesn't look back at this in the future and regret it.
Just one more meph run...

hehe... my gamerscore is almost 50,000... so yes i am a score whore... I dont just do this for no reason however, I join challenges and competitions. Plus, the last 9000 points ive gotten since september were without trying, Ill just look at the list once and hardly try, but I will know that they are there.

Reminds me of that stupid G4 video where it starts out with a guy in a car looking for whores but it turns out he's looking for achievement whores to ramp up his Gamerscore.

Achievements can be a fun to add a challenge or a different way to play a game and can be a nice reward for doing something really crazy and awesome. They can be used to reward players in multiplayer games for being team players or abilities. At the same time however, they are overrated as achievements don't make the game good yet people are obsessed over them like they are entitled to them. Some games don't need achievements and that is okay.
Gamer score on the other hand is entirely worthless in my opinion. All they are good for and obsessively used for is bragging rights and to put other people down. It's a stupid number that people make a big deal out of and are willing to play bad games to earn points just to feel good about themselves. It does not show skill or what type of gamer you are.

I've got a mate who's nearing 40,000 and seems to think its somehow better than my 29K but he's the sort who plays most anything that flickers whereas I have some standards. I mean he's bought onechanbara...

I think the best use is to get players to try all the stuff the developers put in, the play a game on every level, kill an enemy with every weapon etc. Helps you get a broader knowledge of the game and might show you something really awesome