The way this is presented, personhood (which involves behaviours that we'd like a friendly AI to display) is an adaptation based on mutual benefit. We're not nice to other people because kindness and empathy is an unavoidable consequence of intelligence - rather we're nice because we're better off in a society in which we're known to be nice. And that's because we've got fairly limited personal capabilities so are heavily dependent on efficient cooperation with other people.
An intelligent entity without this constraint (e.g. a superintelligence that had access to advanced nanotech and could do pretty much whatever it wanted) w.r.t interactions with humans might not (probably wouldn't?) have any evolutionary pressure towards achieving and maintaining personhood. Which would mean we shouldn't take the approach of "Let's just make an advanced intelligence, because its intelligence will surely mean it behaves with empathy towards us".