Cost, durability, ease of use, and battery of life are some things that come to mind when comparing with your solution. Furthermore, I feel that to be as useful, the helicopter would have to implement autonomous or semi-autonomous control which is not trivial.

How do you make the helicopter rotors so that they don't break the first time they hit something and also don't cut people's faces up. In many situations, have a flying helicopter in a small space can be much more dangerous than a ball on the floor.