Considering how stupid so many Americans are, the rules have to be easy and blanketly appliable to understand.
Instead of "No radiofrequency equipment that operates on 1.57542GHz, 118.0 and 135.975 MHz, 108.1 - 117.95 MHz, etc etc. (And not even getting into harmonics, either), it's much easier to just say, "Hey, moron, turn that crap off."