The problem is that a lot of people actually like how hard it is to sideload content onto an iPhone, because it effectively bricks stolen ones, which is a pretty good deterrent.

Android solves this. Out of the box its locked and can not have software sideloaded. You can disable this feature and do whatever you want but to disable it you have to have the phone open. Stolen phones are still bricked because they can't be unlocked and legitimate owners can do whatever they want.

How is it locked out of the box if you haven't set it up yet?

The bootloader is locked so it won't accept unsigned software. Of course it can't be locked to your google account until you sign in. To unlock the bootloader you have to know the screen code or the google account code.

That same type of control bricks it for you at the OS level when they decide your device is too old (aka you haven't paid them often enough).

No? My old iPad 2 still works and can download apps from the App Store, albeit many apps don't support the iOS 9 it still has since it's super old. Given that it came with iOS 4, i'm happy with the 5 years of updates it got and how it still works.

When will i learn to not engage with the apologists...