But also with GOG you can download the installers and play offline. It’s literally one of their big selling points. It’s less convenient than things like steam, but you can do whatever the hell you want when you buy it. So in that regard, it literally is a purchase. Or as close as you can get with digital goods.
Depends on the game, they still sell DRM games which are limited in being able to be downloaded freely
Same thing applies to Steam. You don’t need to use the Steam DRM if you don’t want to, it gets added by the developers/publishers. There are plenty of DRM-free games on Steam