While I agree multi-user would be nice, I don't necessarily agree it's a good thing for families. A shared device should be treated as such. Don't install or login to apps that you're not okay with the rest of the family accessing.

I'd even argue that children that aren't old enough to have their own device (IMO before high school) don't need a personal profile. And on that tangent, kids shouldn't even use phones/tablets device unless they can responsibly use them.