Well my reason for wanting them is simple. Education. I have a 1.5 year old son that loves things mechanical. Toy gears, toy spinning things. And the bicycle bell I mounted on a chair for him. There is a significant chance he will become an engineer.
This design sounds like a perfect way to teach safety and responsibility to a potential engineer a few years from now. Might even become part of a class science project some day.
Of course he will also be taught safety, that there are sharp edges etc...