Why do growth plates close?

Skeletal maturity: Growth plates are simply areas of the bones through which bone growth occurs. Once we've reached skeletal maturity and we are no longer growing, the bony growth plates will have closed.

So not 100 ft tall!: If your growth plates don't close , you will never stop growing! Hard to buy clothes, and expensive, if you are as tall as the Empire State Building. Could be handy for picking fruit or cleaning skyscraper windows, but otherwise, how would you ever be able to drive a car?