While I too tend to play RTS games single player, most are designed for multiplayer. Most post release changes are based around balancing multiplayer.

There are pleanty of FPS games that are single player, a few the are single player with minimal multiplayer, and other where single player is the after thought.

UT2004 has single player, but it is designed for multiplayer, while FarCry's multiplayer is a side thought.

LAN play enables greater longevity.

I'm not saying this should be a restriction by GoG(because that won't work out well), but a gaming standard - besides modding and open source code once the game has lived its life span.
Any game that has multiplayer should have, at minimal, LAN. That's what I believe. I hear LAN and online Multiplayer is practically the same thing. So that shouldn't be too much to ask.

Also, I like my games to have the possibility to be timeless, since many classics don't have a good modern equivalent.
With the lack of being allowed to have private servers these days, when hosting venues disappear, and when a person's internet goes down. LAN is the main option. I'm happy I can still play Quake 1 multiplayer online(which I do), but if anything went wrong, we can always LAN it up!

Hmm now I need to see if I can get my Rainbow Six 1 and 2 fix.

Nope. A lot of things should happen or would be preferred... the reality of the situation however makes such things unrealistic. GOG is a business, not your friend, and they have never claimed MP is in anyway related to their belief in keeping games DRM free or preserving them.

Games that can come here are already pretty damn limited, limiting them even further would be stupid... only thing I can support is clear documentation on games pages for what types of MP the game supports. That I agree needs work.

^ This.

DRM-free single-player is the basic requirement. Local LAN multiplayer is icing on the cake. Heck, I assume most devs aren't even locking their game on a server out of malice. They have limited ressources and it's probably faster to use in-place libraries and servers like Steam's (probably takes the complexity of things like match-making right out of the equation).

Also, while everything that I've seen so far in terms of multi-player from game having a single-player mode would work in peer-to-peer, devs should have the option to incorporate MMO-like features in multiplayer mode which would require a server.

^ This too.

Funny that you mention this, but I actually never say "PIN Number" (or more correctly in my case, since I'm German) "PIN Nummer".

Maybe I'm alone in this, but I almost always(*) refer to it as "My PIN" ("Meine PIN").

(*) Sometimes I say "Meine Geheimzahl" ("My secret number"), but that's no problem, as you can see - as it has no direct connection with the abbreviation PIN.

Well, an ATM would be "Geldautomat" here in Germany - and has no abbreviation, that I am aware of - so I can't really comment on this.

Are there actually people, that use the term DVD disc?

Because I know no such person.
It's always "The DVD" / "The CD" / "The BluRay" ("Die DVD" / "Die CD" / "Die BluRay")...never is "Disc" attached.

These cases are even worse, because both games did not have an offline single player mode and could no longer be played at all after the servers were shut down. Even if I usually don't care much for the multi player, I agree that it is not ideal that many games today rely on an active server to be played in mp mode.

This, gog really doesn't need any more reasons to reject games.

Just out of curiosity: Hypothetically, would you accept if such games are released on GOG with just the single-player mode (like tons of other single-player only games here) and with its multiplayer completely disabled?

"DVD disc" certainly exists here in Sweden, though with "disc" translated to our "skiva". "DVD:n" (the DVD) can easily be confused as to whether it means the player or the disc, but it differs from person to person, a sentence (fragment) like "put the disc in the DVD" is quite common in my experience, and any 5.25-inch digital disc is very commonly referred to as "CD", or optionally as "CD disc" (and players as "CD player"), especially among the generations that didn't grow up with one of them.

I have no personal experience with ATM or PIN, as the former is "bankomat" and the latter is most commonly "kod(en)" ((the) code).

That's true. I'm also rather amazed by this, as I see more and more developers not implementing LAN multiplayer in their games as a sort of soft drm-alternative. I just hope it won't turn into a "new default" trend.

But I don't see it as a reason to reject a game. I certainly won't buy an online-only multiplayer game if what I'm interested in is in fact the multiplayer part, but some people might.

It's up to GOG to chose which battle they want to fight, and on that subject the answer is clearly no. How multiplayer is done is none of their concern : they are doing their own network for multiplayer after all... and never made a prerequisite of using their own services for anybody.

As long as there's a single player component (preferably campaign oriented and not just some training session to learn the rules), I prefer if there are less restrictions regarding game acquisitions. That said, I also prefer if they prioritize games with a LAN component as opposed those where there's only an online component with additional restrictions.