Wow, I thought this was going to be based on them keeping ballots for too long or something. No one but a close relative or legal guardian can hand in someone's ballots in North Carolina? That's a crazy intense law!
It does make sense though- it makes it much harder to accidentally submit yourself to voter intimidation/fraud.
What kind of intimidation/fraud? Like..."give me your ballot and no one gets hurt"?
Bosses demanding their employees' ballots? I just think the blow-back from that kind of thing being reported to the media would be so massive, no one would be crazy enough to do that. Plenty of states don't have any restriction on this, and I've never heard of such an incident.
I think the best reason is because you shouldn't trust volunteers to properly secure your ballot. But even considering that, it's a huge penalty for something that's totally legal most places (I assume).