The three app stores that are baked into devices (excluding Amazon)
Apple: The exclusive club that allows business transactions on its premises but don't piss off the owners or you're out on your ear.
Google Play: The we accept anyone club where people come to hang out and do a bit of business. Pick pockets and thieves go unnoticed but are thrown out upon discovery.
Windows store: The wild west, lawless, don't trust anyone. A marshall/law bringer comes to town every-so-often, throws out a few trouble makers, doesn't finish cleaning up the place before leaving again.