Have you ever driven interstate east of the Rockies and west of the Mississippi?
If not, you'd be surprised how bare it is. Especially if automation kills the truck stops.
We'll see. The means are trivial for any enterprising farmer, and I think the moral calculus drastically changes once you remove risk to a human driver from the equation.
I'm just saying that the worry about theft is probably overblown. It's almost certainly going to be rare enough that a regular insurance policy will be sufficient protection. People can be hired for exceptional cargo, but that's true today too.