Why would people buy from the legal platform if there's no consequences to using the free platform that's just as convenient? It's really not hard to make a platform that distributes a game, look at Heroic, which is completely volunteer run.

The reason people use services like Steam and GOG over piracy is because piracy requires more work due to legal restrictions. If you legalize it, game studios would respond by putting games entirely (or at least a substantial portion) server side, so there's no way to back up your media. That's absolutely not what I want.

I think it's important to keep piracy illegal, but drastically reduce the penalty so individuals don't get completely screwed if they get caught. That would increase pressure on companies to make their games more accessible and reduce the likelihood that a company would sue someone, but still gives an option if piracy gets out of control.