Personally, I consider not being provided with the install files to be a form of DRM, as it may interfere with your ability to create a back-up copy.
(There's also a case for the requirement of authentication of payment, but I'm not willing to go that far.)
Do you consider games distributed as plain no-installer zip files to be DRM'd as well? What if you went to a website and got the instruction "download these files and put them in this [described] folder structure"? I don't see the difference between that and a DRM-free Steam game except the method of distribution (client versus web site).
Then again, I consider DRM to inhibit your usage of the data (say, when you need to be online to install, or play a singleplayer or LAN game), not the acquisition thereof (say GOG, Gamersgate's or Steam's DRM-free games).