USA long-time motorcycle owner here: agree. I believe there have been laws on the books for many years regarding noise limits, but they are (effectively) NEVER enforced. No-muffler-at-all ("straight-pipe") exhausts on V-twin (EX: Harley Davidson and its countless clones) are de facto standard (and for reasons unclear to me are accepted).

Also, aftermarket exhaust systems for motorcycles (99.9% of these being much louder than stock/OEM) are a huge business: I'd guesstimate that 50% of motorcycles sold in the USA soon (< 1 year old) end up running aftermarket exhaust systems; it's a standard first modification done by almost all enthusiast owners.

> it's a standard first modification done by almost all enthusiast owners.

Since laws are unenforced, it's also possible for dealers to upsell louder exhausts without even needing to visit a 3rd party shop.

About the same as for leaf blowers.

Anecdotally I've heard that they are mostly used as a way to stop riced out Japanese cars.

Not ppl on motorcycles. As someone who has run straight pipes across two major cities never had an issue. A bunch of motorcyclists don't even have licenses lol.