I imagine most people don't even know when a new release releases on GOG platforms because 90% of the time that's not the case. I know I don't check GOG every time a new game releases. I'd have to know before-hand for me to buy there.

And that was kinda my point. When most of the games don't release on GOG there's very little point in trying to build a library on GOG because you can't depend solely on GOG. You're going to have to split your library and most people prefer to have all their games in one place.