> At least one reason might be backup communication when jammed. Line of sight might allow for direct laser communication (either to the piloted plane or a nearby relay to retain some stealth) in the case of radio spectrum jamming.

This is precisely why. Iran has shown that it can, on some level, interfere with long-range communications of drones. I'm sure the Chinese have even more such capability. Having a C&C platform within the same battlespace limits communication exposure.