Bee keepers move comb in and out of the hive frequently during the producing seasons. If they just cut the caps (top layer of wax) off the honeycomb, drain it, and then put the comb back in the hive, the bees have to use less energy to make comb, so they make more honey. If you put an “empty frame” (a spot with no honeycomb already on it) it takes the bees a lot more energy to make the comb so there is less honey. So it’s a trade off from the bee keepers’ perspective.