Indeed there's no benefit to users from an app being arbitrarily tied to the Play Store, but that's entirely equivalently so to how there's no benefit to users from any sort of DRM.
Perhaps "digital rights management" isn't exactly the thing to use here, but it's still the same general concept of "author of a specific piece of media/content/app adds an arbitrary technological restriction that doesn't directly benefit users in any way (while ideally not affecting intended proper users) but still potentially helps the author".
It's harder to see for free apps, but for paid ones it's utterly trivial - of course you're gonna have to buy it through the Play Store with a Google account if the author has decided to only sell it on the Play Store; and afterwards wanting to use it without Google Play interference is equivalent to wanting to access media without DRM after having bought it (i.e. reasonable desire, perhaps not even illegal to attempt to achieve through arbitrary means, but owners of the respective thing can still try their damnedest to prevent you from it).
Well, here the app authors as well gain very little, they usually enable it just because they want the maximum "security", and are led to believe that this will help we with that
Perhaps "digital rights management" isn't exactly the thing to use here, but it's still the same general concept of "author of a specific piece of media/content/app adds an arbitrary technological restriction that doesn't directly benefit users in any way (while ideally not affecting intended proper users) but still potentially helps the author".
It's harder to see for free apps, but for paid ones it's utterly trivial - of course you're gonna have to buy it through the Play Store with a Google account if the author has decided to only sell it on the Play Store; and afterwards wanting to use it without Google Play interference is equivalent to wanting to access media without DRM after having bought it (i.e. reasonable desire, perhaps not even illegal to attempt to achieve through arbitrary means, but owners of the respective thing can still try their damnedest to prevent you from it).