My own negative experiences with Steam vs GOG were:
- Moving homes and having no landline Internet for a while and not being able to most install most of my Steam games on my desktop gaming PC because mobile Internet is slow and expensive so installing a big game literally costs money. With GOG I just downloaded the offline installer at work into a USB Flash Disk and then installed it on my desktop at home.
- Not being able to install perfectly functional games from Steam into a machine with an old Windows version because the Steam client didn't support it anymore (even though the games were compatible with that version). Mind you, you that machine shouldn't even be connected to the Internet for safety reasons, which again would stop me from installing games from Steam even if the client worked.
Beyond that with Steam you have the risk that Steam takes away one or more of your game for some reason (say, licensing problems or just Payment Processors pressuring them to do it), you lose access to your account and can't recover it (unusual, but possible), your account is forcibly closed for an arbitrary reason with no appeal (not happened yet with Steam but did happen with others such as Google), the store goes bankrupt and closes (not happened yet with steam but has happened with sellers of music with DRM if I remember it correctly), games without DRM or with Steam's light DRM (the one simply using steam_api.dll, for which there are implementations which just emulate the API without phoning home) get forcibly updated to hard DRM so whilst before you could run it offline, now you can't.
(Mind you, you get some of these problems - such as risking the loss of your entire game collection if the store goes belly up - with GOG if you just use GOG Galaxy and don't download the offline installers for all your games, but at least there it's entirely down to you as the store does nothing to make it harder for you to eliminate those risks)
Steam makes a lot of effort to keep itself inside the loop of gamers playing the games, not forcibly so (as somebody pointed out, they don't force developers to use DRM) but more with a soft sales push (they offer it for free to developers and publishers and purposefully a bunch of "easy to implement" online features such as Achievements to using the "phone home" Steam DRM to induce developers to use it). They also do not at all indicate before a purchase on the Steam store if a game has Steam DRM or not, so that consumers have to go out of their way to make an informed buying decision, if at all possible. Even for the games on Steam without any DRM one has to actually use an unsupported process to keep a copy of that game after installed from Steam (a simple copy & paste which those who know what a filesystem is can do, though maybe not the less tech literate, though gamers tend to be more tech literate), so people tend not to do it. The result is that most Steam games have DRM and most game playing done on games from Steam involves the phone-home check of the Steam DRM.
Meanwhile in GOG it's the exact opposite - people have to really go crazily out of their way to run a game from GOG with DRM (apparently there are one or two which slipped the net, and for others I guess you could implement your own DRM around it by encrypting the binary or something ๐)
Ultimately it boils down to weather one is comfortable or not with having for their games collection the risks I listed above.
Personally, with my almost 4 decades experience as a gamer (and almost that much as a Techie), I'm not at all comfortable with that since over the years I've seen multiple instances of people getting fucked by their software or even hardware being unnecessarily tied to a vendor for their normal usage loop.
That said, people going into this aware of the risks and still cool with them, then, hey, ๐, you're an adult, making a well informed decision and will only affect yourself it the risks do materialized into a problem, so you'll get no criticism from me.