Why are Harley's Deafening Rumbles Ignored?

Why do police or whomever is in charge of noise pollution not interested in cite motorcyclist. Other than concerts I don't think loud is cool. Don't even try to say the cops have better things to do, because I regularly see them standing in groups of three or four "shooting the shit" and carousing while we pay their salary.

Would I challange this? Never I get enough trivial citations and I spend most of my time hiding from the police.