To use a more readily recognizable name... It would be like seeing a post about a new version of Windows releasing, and someone saying "Great! Where can I get the source so I can roll my own?" Maybe that person wouldn't know... But the assumption is going to be they're making a comment rather than asking a genuine question.
In my experience the steam client is physically painful to use (unpausable downloads, cache verifications, slow startup, unresponsive store). It's not as bad as iTunes, but it's getting there.
Is there an easy way to filter games by this criteria on Steam itself?
Yeah, they get more by shoehorning people into Steam than they would lose from not selling DRM-free versions.
There may have been a point to stop this from growing into what it's become early on... But it's too far gone to be broken free of save a major scandal. And even then, it'd probably take a few. It's just by far and large a non-invasive tool. They've worked out many kinks.
I'm not saying it's perfect, nor am I saying we should be happy with it. But it's avoided the major problems most other DRM efforts see in "making things more difficult for legit users than pirates". I haven't had any issues with any aspects in years.
I understand that Valve can be already too involved with game producing companies which still have backwards thinking that DRM is a must. But Valve can start pushing them to drop it, instead of being passive.