> They don't because too many people pirate games to make that a viable business.
Given how many games on Steam are sold either DRM free (you can just transfer the files over to another PC and they just work) or functionally DRM free (Steam's DRM is trivially bypassed, so one step removed from DRM free), this doesn't really scan. Other than games with Denuvo and multiplayer games, DRM is a non-issue for actual pirates.
It seems a lot more likely to me that the people in charge will have a fit at the idea of releasing the games DRM free, but don't actually care to know anything about the details. So long as the DRM checkbox is ticked, and they don't know about the fact that Steam's DRM is trivially bypassed, everybody mostly gets what they want.