I wonder if the worry ends up being about losing organizational depth if you get into the call up game, kind of like how they lost Forsberg on waivers a couple years back. Not that anyone is picking up Campbell, but maybe they lose Pickard or Rodrigue on waivers. That's the only hesitance I can see there.
But ultimately it isn't fair to Campbell or the team to keep rolling him out there when he's performing like this. It's just sad.