Earlier quoted context omitted.
For me, it's that my 20 year old account has games I bought 20 years ago. I can trust that anything I purchase from Steam will be around for a long time. No other company has demonstrated that kind of reliability, except maybe Apple. Plus, I think Steam is a superior product. That being said, I also try to buy on GoG as much as possible, since I really prefer to have DRM-free games and I want some competition in the…
> I can trust that anything I purchase from Steam will be around for a long time. Unless the publisher pulls it or pushes an update cutting music because of license deals expiring. Or gets a stealthy replacement with a worse remaster. Or your OS drops 32 bit / x86 support.
Steam provides the game. It "will be around for a long time."
It is not Steams job to ensure the game runs on every device or OS version for eternity however. That is up to the publisher of the game.
If you install Steam on an older version of the OS that does have 32bit/x86 support, Steam does its job.
I do think however that Steam should add clarification to the "game requirements" to specify OS version or hardware however.