I can’t even see much of the cargo holds from the ground, and I’m sure it would be some kind of H&S violation if I tried to climb up in there while loading was in progress.
More importantly, what are you supposed to be checking? I haven’t been trained in the difference between correctly packaged/stowed freight and otherwise, especially at the ULD scale, and I doubt many pilots have. I get a loading certificate and NOTOC, and that obviates me from putting my hat on and peering into the hold going “Yes, very good! Lovely work! Carry on chaps!"