They tolerate those because they open when someone runs their game through Steam. How many people purchase through those platforms though?

I don't think that's true. When they open when a game runs through Steam, that's when they are especially annoying and not tolerated. But there's plenty of people just buying Assassin's Creed on Uplay or Fifa or Need for Speed or whatever on Origin (maybe ea wasn't a good example in current times).

And what does that have to do with what I’m saying?

Well you claimed this would not happen. I'm saying that, if these shit ass tier stores can manage to have a userbase, I'm sure a better store with features comparable with Steam would get a bigger userbase.