Steam is its own DRM on top of whatever else a developer chooses to do. I found this out one year when I spent months without internet access. At a certain point steam would refuse to run any of the locally installed single player games I had paid for through their platform until my computer phoned home to their servers. I'd already configured everything for working offline and they did successfully for a long time until one day they just wouldn't anymore.

If you don't want lose access to every game you fully paid for on Steam you'd better pirate a copy of everything you bought because on a whim they can take it all from you at any time.