I don't use steam at all either.
GOG is completely different story, I did buy 30+ games there.
For me the difference is DRM-free packaging, so I can have my own offline backups of installs, and I don't have to run some resident weird piece of SW which is checking my PC and stuff while I want just to run some stupid game (= steam client), it's basically so similar to malware, that anyone hijacking steam control servers would have serious botnet available within minutes. I don't like that idea, after all, it's just computer games, nothing important.