I think most people also do not care that much about the whole drm thing and have no problem just installing what is mostly known and used for pc gaming nowadays. The same way also a lot of people do not mind installing every launcher the publishers throw at them. I am open for other options if they make sense, but what we have for game launchers at the moment strikes me the same way as the billion streaming sites every company owner wanted a bite of the cake from. It can be bad to be on both sides of the scale, I would say.
Itch.io not only has no drm, but is rather more niche. There are a lot of thoughts going into publishing on "yet another" storefront for a developer/publisher, so unless it hasn't been forced onto you or gained somewhat mainstream appeal, most will not use it. GOG is another good example: It wasn't known that well unless you specifically looked for a good site to find old (and working) games. Since then it became wider known, partly because of the company behind it, partly because it expanded to also include new and indie titles. But still, it is mostly a question if "new game xyz" comes to the platform, either because the publisher doesn't want to tend to an additional platform and calculate the profit, alongside having to take care of another (drm-free) build, or because the game is already stuck on one of the other publisher-owned launchers, among it just not being that publicly used compared to steam/consoles. Which looks like a self-repeating cycle at that point.