That is true - the publishers/developers incorporate the Steam DRM code into their game executables, which make the Steam client and its restrictions a requirement to run their games. As you say, there are a few games that don't use Steam DRM but use Steam just as a content delivery system. I don't know who makes the decision to incorporate Steam DRM into each game, but I really doubt that Valve forces the publishers/developers to do so, so from a "moral" point of view (although not a technical one) I agree that it's the games themselves (i.e. their publishers/developers) that enforce the DRM.
People think 'oh they just want to put DRM in and restrict the games' and get mad but there are actually other reasons for it.
This is getting a bit off on a tangent but it seems that some developers like the Steam integration because it puts the load on Valve's servers and not their own and/or the Steamworks cloud save, achievment etc intergration.
There's an interesting post about it on the General Steam forum by way of Stardock's Sins of a Solar Empire forums. http://forums.steamp...d.php?t=2748423 These posts are from Frogboy, AKA Brad Wardell, the founder, President, and CEO of Stardock.
As it had turned out, our fears have been unwarranted. Impulse, now owned by Gamestop, pays like clock work and so does Steam. By contrast, with a retail distributor you were lucky to get paid merely 90 days late. And that’s not counting the obnoxious and expensive RMA games they play. I like the service Steam provides. They’re easy to work with, they’re honest, and they’re passionate about what they do. And most importantly, they let me, as a game developer, focus on what matters: making games.
When you use Steamworks, you're making a trade off. You will lose some customers. Similarly, not having your game at retail is a trade off. It's one we made with Sins of a Solar Empire: Rebellion. We lost vastly **vastly** more sales not having it at retail than we did by using Steamworks. But the trade-off was that we were able to have a release date of our own choosing and frankly, if I have to choose between money and having a universally beloved game people like, I'm going to choose the latter every time.
Personally, I don't like games requiring to use Steam. But, as a developer, my options are to either spend hundreds of thousands of dollars developing stuff ourselves or letting Steam do it.
The only reason Elemental isn't using Steamworks is because I personally vetoed it. The IT team just hates having to keep running the rather expensive infrastructure we have to add, update, and deliver games to users. They'd rather hand it all over to Steam and be done with it so that they can focus on other things. That's the trade off we're facing.
The DRM thing that I've seen people mention is meaningless. That's not the reason companies use Steam. They use it because Valve is willing, for free, to handle all the updating and distribution. It costs us about $10k per month just for Sins of a Solar Empire dedicated bandwidth for the hundreds of thousands of users who are updating its various versions or reinstalling it each month. That's a lot of money when Valve is ready to handle all that for free. And that's just the bandwidth. Forget all the people involved that have to get the files updated, test the updates, handle customer issues, etc.