Unfortunately, Steam has indeed engaged in some degree of "rug-pulling". Their client has locked out older OSes, and thus prevented users from continuing to be able to play the games they purchased for those given OSes.
I've been on Steam since 2004, just a few months after it launched, and I have purchased some ~600 titles on there since that time. Of course, there are countless titles that are no longer playable because Steam will no longer run on the OSes some of the earliest titles were designed for. In some cases the titles will run in a newer version of Windows, but a computer that initially ran Windows XP can't realistically be upgraded to Windows 10.
I still have ~every computer I've ever owned, and that includes the one I originally ran Steam on. So, after buying a ton of games, nothing changed on my end, but Valve decided to end access to my purchases because they decided I need to buy a new computer so I can continue to play what already ran just fine since 2004.
There was quite a long time that I didn't foresee this inevitability with Steam and purchased a ton of games, but now I only buy them on steep discount because I know I'm only getting a "temporary pass" to play them until Valve decides my computer is too old.
Oh yeah needless to say, GOG is awesome in this regard. All my purchases are backed up on my NAS. I can play them on my Windows XP/7 computers if I want to. As much as it's a hassle to store all that stuff (and not have cool social/network features like Steam does), at least I can keep and play my games as long as I want, without limitation.