you do realise that valve do not actively seek out games to put on Steam? They are not "coming" after anything at all, it is various publishers who realise that there is a market for re-release of classics (partly due to gOg's success), and they try to flog them on the largest platform.

(and TET have already said that for them the well of classic games have dried up, so...I guess Clans failed the "Moby Score" test)

Of course Valve is not stopping them putting classics on Steam, that would be rather silly, but they are not coming after them either.

An all new low: calling laziness a feature :D They just looked at their old games, found this one tested it: hey it works but no music because that would require a days work. But what's this? If we put in a different cd, music plays..., let's show the error using a screenshot, call it a feature and profit :D

If GOG turned this down, I assume it's at least partly because of the music situation--although this game did get pretty lousy reviews.

Half-Life (1998), Opposing Force (1999), Gunman Chronicles (1999), Sudden Strike (2000), Cossacks (2001-2002), Metal Fatigue (2000), Turok 2 (1999), Kingpin (1999) to name a few.

By 1999/2000 red book audio was still perfectly common. I don't know when game developers really started using mp3s and oggs but the earliest examples I recall are from 2001 (like Operation Flashpoint), but I'm quite certain that by 1999 devs still pretty much had the choice to either use a tracker format (like Unreal, Deux Ex, NOLF and Gothic did), uncompressed audio files (which usually meant crappy quality, e.g. 22khz resolution) or CD tracks.

Probably Valve dont seek them...but doesnt opposes to release them as well. Ok, lets not call it "forceful growth in new markets", its more like "black-hole gravitation collapse", when Steam become THAT big so all games starting to fly\being sucked\fall in on their own. And nothing alive outside of Steam OFC.
Anyway, i more curious which next market will start to melt in Steam? Maybe Android games?

Why should they?

Dunno, to keep some type of certain image of store? Like GOG is "classic and old-school".
Earlier Steam was AAA store, now..."everything store"?

Steam has always been a Game store. They pushed indies from before it was hip. Their image is "VIdeo Games".

Great, lets all vote to sell GOG to Steam already.

which I was not saying at all...

Well they are upfront about it, I mean it's the first thing you clearly see when visiting the store page. I actually like that, show the biggest issue the game's got straight away so you don't cheat your customers.

I know, i just pushing it to absurd.
Its not like i cannot see that Steam made a lot for Indies, they really did and for Linux gaming, for example, too (like Humble Bundle), but...there is always limit of harmonic growth. Like i splitting cell in your organism can turn into cancer (hope, never), then Steam become closer and closer to Monopoly. And i dont see anything good into absence of choice where to get my stuff.

That is another matter, and a problem with free enterprise. However, it does now mean "Big bad Steam is out to get everyone else, crush their bones and drink their blood!". I do not fear any absence of choice, as there is quite a large market outside of steam also. You can not really blame them for creating a tool that publishers and developers actually want to use...

I recently played Quake 1 + expansions and Quake 2. I noticed too late that Steam has no music for those games...

This is the solution.
Yes, it's japanese but the program is in english if your Windows isn't in japanese locale.

This instructions work for Quake 1. (If you have steamophobia you shouldn't click this link.)
To get it working with Quake 2 I had to try around a bit. I'm not sure anymore what exactly I did, but it worked. ^^