I've always felt Valve's numbers are misleading. I would like more hard stats from them. I don't think Valve is as nearly as popular as the big 3 in North America. Instead I think Steam gets a lot of users in places like Russia where consoles are not readily available.
Also, I personally don't use Steam. If I do get a PC game it has always been from gog.com. Given the rise of the Epic Games store, I might consider them as well. So you can count me as the type of person who might use the Epic Games store but not Steam.