We've barely been able to get people to stop referring to all Android devices as "Droids". The average person doesn't even know about alternate app stores, yet alone have the will to seek them out, install them, search for an app, and then pay for it (likely having to enter payment info this time). You might as well tell developers to release their apps on the dark web.

I'm sure you can release niche apps on these stores, but the general market isn't moving away from the Play Store any time soon, and that's where the money is.