Why is it a bad thing for you that other’s get to use their phones have they see it fit after paying for it quite a bit, while the whole thing won’t case any difference to you?
A program that phones home often with tracking data, thus keeping a data connection open and the processor from sleeping would absolutely have an impact on battery life and longevity. This would be code that Apple would normally block at the AppStore level.
And we saw how mad people were when Apple slowed down processing speeds to extend battery life. Can you imagine the outrage if Apple suddenly said that your battery is no longer under warranty because you installed the Facebook app directly from Facebook?
There are good reasons to disallow any third party applications on some platforms like cars, but apple allows it and they only have a quick look at applications. The real security is in their sandbox/API.
I mean, that’s effectively where this whole argument leads. You could imagine a scenario where using external software could damage things like your battery, so now the user is on their own.
I don’t think that’s a tenable option either.
This is effectively what Google does with Chromebooks and developer mode. But if you’ve enabled developer mode, can’t you go back? But when you get into trouble, you can revert back to the base install (and lose all other data). Again, that’s not a good option either as people would complain about that too.