I’ve seen data from Austria indicating that 70% of vehicles exceeding legal noise levers are motorbikes, 20% are cars, 10% are trucks and busses. Vast majority of loud vehicles are modified in purpose to make more noise.

Also, loud vehicles will not pass annual technical checks so people put in legal exhaust for the check and then put the illegal, loud one in again. This has nothing to do with people not having money to fix their cars/motorbikes and everything with low IQ street racing sub-culture.