Its lemons, the cars are $500 shitboxes that the teams generally don’t give a shit about. So they do stupid things to them for fun. Or because they were drunk and it seemed like a good idea at the time. Or some combination.
There are extra awards for themes and stuff for the race teams. Attempting to knock off famous race liveries that are vaguely relavent to your car of choice with rattle cans is a common one.