Linux by design gives the user enough rope to hang themselves with.

And that's certainly not a problem when dealing with tech enthusiasts who know what, when and where to touch to avoid messing things up. But when you're dealing with getting a phone into the hands of ordinary people, that isn't going to fly because all of those people will at some point start mucking around inside and then expect tech support when they mess up.

For mainstream adoption, the linux kernel must and the desktop environment must be at least somewhat locked down.