> They all have DRM which make it essentially encrypted with no decryption service available.

Not all do. Games for a lot of systems can be read directly from the storage media.

> Likewise, the game isn’t usually 100% contained on disc.

Only for the couple most-recent generations. But even virtually all of my PS4 games (not to mention earlier generations) are actually on the disc, playable without a download.

> So the question in my mind becomes, do game companies have an obligation to support games in perpetuity? I think when phrased that way, the answer is an obvious no.

Agreed, but I also think that if they don't have that obligation, then society doesn't have the obligation to provide copyright protection when they drop support.