Many, if not most, major games these days require online activation. This renders hardcopy versus digital moot as far as "owning" a game goes.
Not necessarily, there is a case to be made that you have more legal protection with a store-bought physical disc than a download if you choose to violate the EULA for whatever reason. I mean, depending on the court it could end up meaning jack-diddly-squat, but there is a difference in point of sale purchase laws for downloads and physical media.
As for Steam I am sure I commented before but my whole thought process is that DRM is impotent, it's a non-issue, it might as well not exist. Why companies keep using it I have no idea and I feel like it drives more people to piracy than it could ever stop (since it stops no one), but whatever... on an open platform it's completely irrelevant. If for some reason someday Valve or whoever else decide to take my account away I'll look at my games shelf, find the boxes for all the Steamworks games, then pirate the shit out of all of them and burn new DRM-free discs. Problem solved.
In the meantime Steam is annoying sometimes but is mostly harmless, and it's good for multiplayer.