You're assuming that the system accepts that each room will be full which is not the case. The system assumes the average occupancy will be lower than the max but assumes the max will be based on the upper limit of occupancy, not stuffing. That some will have less is already factored in so it's not applicable to the argument. The big deal is that there are REAL costs (both $$$ and otherwise) to such issues including pool use, parking, restaurants, extra maint, etc. And while there are other areas where there are also extra costs, each issue stands on it's own. So that one person won't use the pool or won't drive does not act as a credit for those stuffing. Besides, to do so on the sly is simply dishonest.
You know that for a fact the system assumes the average occupancy is under the max? Again I don't really think what anyone on here says is going to make a difference. If I want to put 6 in a studio, I will. If I don't, I won't.