This would mean that there's only two app stores: Apple's and Google's.
Google doesn't do that because that would be an abuse of their market position and they would get rinsed in the courts. Since the same laws apply to Google as Apple, and Apple clearly has significant market power in smartphone and tablet computers, it stands to reason that Apple should be prohibited from doing the same thing.
Are you sure that Google doesn't do that because the Android platform is an extremely viable and lucrative alternative to iPhones, and that people who value the ability to sideload software on their smartphones flock to Android for precisely this reason?
As far as I can see, what distinguishes Apple from Google is status quo. Apple never did allow app distribution other than through the Apple App Store. i.e. "We've always been doing it"
That's what I'm getting at. Is it anticompetitive to deliberately make your product worse by removing a key differentiator between your product and its closest competitor?
Or come at it from another angle: would it be "anticompetitive" for Apple to (in new iPhones) completely remove the App Store and thus all reasonable expectation to be able to run third-party software? Is it anticompetitive to sell a handheld computer than can do email, play music and videos, etc., but not run third-party software?
Is F-Droid in Google Play ?
It is not.
For every update, times every app you have to click through a stupid screen "Are you sure you want to install this update? It requires no special permissions."
With auto updates this was quite a wakeup call...
Another nice thing is F-Droid listing multiple versions, another thing sorely lacking in Google Play.