I download 0 new apps per year, but I use WhatsApp, Outlook, and Google Maps. Today, I get them all from one store - one password to remember, one credit card to have, one stupid set of "security questions" to forget the answers.
Tomorrow, Facebook AppStore will be the only place to get WhatsApp, Microsoft AppStore will be the only place to get Outlook, and Google AppStore will be the only place to get Google Maps, so I will need to download n app stores to get to where I am today. Create n accounts... accept n privacy policies... activate two-factor n times...
Yeah, no, thank you but no. I'm pretty happy with the AppStore as it is, thank you very much.
Also consider the market share of iOS and Android. Why bother for such small amount of price sensitive users?
iOS is another story entirely. The App Store has a lot of demands on the app developers wrt. UX, compatibility, etc; there's a lot of money to be saved (and faster time to market gained) by not publishing apps there. And then you can also bypass the security/privacy screening.
There is competition amongst stores and people outright reject software that is exclusive to a store that they do not favor.
That's a funny thing to tell to your kid that he's now an outcast in his school because everyone plays that Battlefield game — but his dad "does not favor" EA.
But what you won’t be is under the thumb of a single company that has way too much power over you.
But I like Cheez-its, and Cheez-its are NOT USDA organic and the supply chain is full of modern monoculture farmed grain and its full of artificial ingredients. The store refuses to carry it. It's not nice! I like those, why can't I buy them there?
Even if it was the only store in town, and if I live in Anytown I have to shop at the fancy-pants health store, I chose to live in Anytown. I can leave anytime I want. But wait! There are parts of Anytown I really like! It's walkable, and quiet, and safe. I just can't have Cheez-its. It's not nice to make me choose between all of the things I like, and the things I don't! I want to have my cake and eat it to, or, rather, in this case, my Cheez-its.
So say you want WhatsApp on your phone.
Today: AppStore - get WhatsApp.
Tomorrow: AppStore - get Facebook store - start Facebook store - get WhatsApp.
The power Facebook (also, Microsoft and Google) have over the users of their apps may be so great that they could pull it.
Small companies? No chance in hell.
So actually, this move might put Apple (and Apple users) into a weaker situation while empowering FB/MS/GOOG and having no effect whatsoever on small app developers.