My guess is that Netflix couldn't negotiate agreements for a lot of the content that makes the service attractive without relenting on DRM. We'll know when Netflix turns evil, because it will force you to sit through commercials and previews before showing you the content you want and paid to see.
I think you are absolutely right. It's not content providers that are pushing for DRM, it's content producers. There's absolutely no way a rightsholder would let Netflix show their content if, god forbid, there was any remote possibility that a user could download and use their content outside of a controlled environment.
In some ways it parallels internet piracy. ISPs for the most part are sick of policing their users and sending out C&D letters for copyright infringement, but they more or less have to due to pressure from major studios.
