Because there aren't 100 separate wifi channels (frequencies) so if you put big powerful routers with lots of signal then people from the other end of the room

Because there aren't 100 separate wifi channels (frequencies) so if you put big powerful routers with lots of signal then people from the other end of the room will try and connect, if you put little low power ones then they intefere with each other. Then you have the overhead of 1000s of people trying to connect, their wifi cards not receiving a response because the router is busy so they try on another channel tying that one up as well. Wifi really isn't designed for this sort of setup - it's amazingly difficult to get it right, throwing hardware just makes it worse