There are many reasons.
1) Some people don't like DRM in any way, shape or form. Steam is DRM no matter what Gabe likes to say.
2) Many Europeans detest it because Steam fleeces us by converting $1 to €1. This can mean paying up to double the retail price. Australians get hosed even harder.
3) Publishers are allowed to maintain RRP on Steam while retail stores have put games in the bargain bin. Case in point Vampire: The Masquerade Bloodlines = €19.99
Personally I am ambivalent. It's not perfect and I even had my account suspended which included all my games over a mistake, however it's not the worst solution. That would be UbiDRM.

1) Its one of the best forms of DRM imo, It doesnt put many restrictions on you and I like the features it has (the over-lay, auto updates and steam cloud). It seems pointless complaining about it.
2) That is a problem but it wont effect buying retail games that need Steam like OP is complaining about
3) Thats true. but Steam also have lots of cheap games and tons of sales. No one is forcing you to buy the over priced version (You don't buy every thing in the same shop do you?)

1) Yes it is but it has serious drawbacks. If your account is suspended you lose every game you ever bought on Steam. This happened to me. It wasn't fun as Valve employ a team of chimps to handle customer service.
2) Does not affect retail Steamworks games that is true. Unless the person does not have net access. Then the Retail game is completely useless. Don't say everyone has net access as it's simply not true.
3) I gave the example of Bloodlines for a very good reason. It's not available at retail anywhere. The only place you can buy it is online and on Steam that price never changes from €19.99. Why? Because thats what Activision want for it and they know it will sell on name alone. Thats why Bloodlines is never in a sale.

There's no reason to have a problem with Steam... until you have a problem with it. Unfortunately the client is hardly bug-free and its policies and management could be better also. Having your entire account suspended because your credit card company made a routine enquiry about a single game you purchased is hardly the kind of problem you can overlook now, is it?

1:a disk check vs steam. I would take a disk check over steam any day of the week.have you played battle for middle earth one or two?Guess what they had something you could click on to patch up your game.If your friend[s] does not use steam for any reason. You can't talk to her/him with it now can you. All your games are tied to one account. Boom one ban and 200 games all gone in a flash.
2:nothing much to say about that.
3:yes which before a sale are just as costly if not more so then retail.Woot for paying more for no box no disk and no manual. Best of all paying 50-60 bucks for a game i can't say i own.