Probably more feasible for some of them than buying a new phone, at least.

I think every device should ship with root by default, it's the case for computers, I don't see why phones would be any different.

Because computers don't come with an app store that contains tonnes of crapware. Even if they did, people would install a smaller variety of apps.

I see phone repair shops at every street corner, I don't see why they could not offer this as a service.