SteamWorks isn't tied to the Steam shop. VALVe usually offers a standard distribution agreement when giving away the SteamWorks API. SteamWorks is free to use and most developers/publishers also sign on the distribution agreement. So far there is only one exception.
During the development of Supreme Commander 2, GPG had to decide which online multiplayer platform should be used. Their options were basically their old GPGnet client, Games for Windows Live and SteamWorks. They decided to use SteamWorks. There was no pressure from VALVe or anything like that.
Or look at Modern Warfare 2. It's distributed over Steam and uses Steam as DRM. However, it does not use SteamWorks. It uses its own multiplayer solution.
Yeah, and these Steam sales are hard for people to resist. I have trouble persuading people as to the dangers of a Steam monopoly when Steam has frequent, incredible sales. How can I persuade users to purchase a game on a competing service if Steam has it on sale for 60% cheaper? Most people will follow the money.
Peope have to be careful with Steam sales. They look juicy, but often times some of the games are or were already cheaper in other stores.
"Blah blah, who cares, I don't have to deal with DVDs anymore!" I've never really understood this argument. Seriously - other than the .000001 percent inconvenience of having to treat your possessions with a bit more love and care than a 2 year old, what really is the big deal? I use Impulse, but never for this reason.
For some it's a matter of principle
. I for one find optical data mediums incredibly outdated and inconvenient. Why would you want to go through all that trouble of physically getting an object with data on it, when you can have it directly over the network (unless of course you don't have internet or just very slow internet). I abhor optical discs. That's why I am also reluctant to buy a Blu-Ray drive, since this is "ancient" technology. Why should I go through all the hassle of handling an optical disc, using a dedicated Blu-Ray player (Hardware or Software), getting annoyed by menus etc. when I can have the movie or tv show directly from the network without any trouble?
Sure, some like to have a box and I can understand that. But generally I follow the Star Trek principle, where virtually every data is available to you everywhere through LCARS