In my experience (YMMV, I've a long history of gaming), if steam disappears I'll be disappointed to lose my titles, but it won't be the end of the world. Games I've played yesteryear rarely hold up over time - the vast majority I've fired up again feel very dated. And there's always a ton of new, interesting, and cheap games coming forward. Games are somewhat ephemeral/disposable, I find, so the "won't be around in five years" is less of a problem than for other software.

Again, that's my use case, others may differ.

It really depends on the games. The vast majority won't even be interesting after a year, but there's a few gems that are timeless.

Although those are also the games that tend to get regular remakes; while I still have my Final Fantasy VII disks for Playstation 1 I'd rather fire up the Steam port than mess around with an emulator. Or OpenXcom rather than the DOXBox'd original.

People still play Star Craft:Brood War as a profession. And I still like to play Master of Magic or Doom 2 from time to time. GOG.com made business on these kinds of games, so I'm not alone.

DRMs and always-online requirements are sad and I hope they go away.

Steam's DRM is opt-in too, not all games distributed via Steam actually use it.

Yeah, Steam is also not an angel. But right now it gets us something we need deeply: Playing on a free OS. Let's worry about the next step after that one succeeded.