Nothin’s “wrong with” them, except that they make you look like a puerile, pubescent “Beavis-and-Butthead” type, who hasn’t matured enough not to laugh out loud at your own flatulence.
“He-heh. He said ‘flatulence’. He-heh.”
If that’s how you want to be perceived, have at it, but don’t go around thinkin’ you’ll get any respect. People will take one look at the butt end of your rig, and blow you off as a persistent adolescent.
The bumper nutz are on the trucks, but the pricks are in office.