There are ten thirsty people and a drum of ten gallons of water how much can each person have? Assuming they play fair of course.
Now work it out if there are 100 people and the same amount of water.
Now think of forage availability and hive numbers, same same, rocket science it is not.
More some 70 years ago a bee farmer, one Manley by name said in one of his books the only way to find out how good a site was, was to install hives and monitor for five years. If on increasing the hive numbers the take decreased then guess what, you had reached maximum density.
Urban beekeeping is fraught with extra risks compared to my rural methods. More people to object, more chimneys for that unexpected swarm to vanish down, and less forage. Before you bridle and yell but the countryside is a desert, then I have a better countryside than you do. 🙂 Mine has plenty of forage, more than enough for my hives.
The numbers game you see is one that can backfire on one.