I think the thing with motorbikes is everything is so much more exposed, and they rev higher in general, so the sound thing is probably a harder problem.
I am actually of the belief that motorbikes and scooters should be encouraged in cities, because they are a lot smaller, and more efficient in general than cars (so long as you don't have a massive bike), and take up a lot less space when parking. Do most people really need a 1.5 tonne car to go to work as opposed to a 200kg bike?
Meh. Some have figured a way to make them quiet. Most "touring" bikes are very reasonable. I'm thinking BMW K16s, Honda Goldwings, Yamaha FJRs. With stock pipes, of course. Hell, even my VFR1200 is very quiet with the stock pipe, which closes a flap below 5000 RPM. When idling at a traffic light, if there's a car around, I can't hear the bike.
You inspired me to exchange my Akrapovič (came with the bike when I bought it) to the stock pipe (which also came with the bike).
I find that their exhaust smells much worse though, especially scooters.
Source?
I live in Paris, a few meters from the busiest crossroad of the city, and my experience with scooters (even the best 4 stroke ones) is very, very different.
[BMW made a cruiser bike for a few years. They were trying to move into Harley’s market segment. In order to get the “right” sound they had to detune the engine, resulting in a massive decrease in horsepower.]
https://www.bmwmotorcycles.com/en/models/heritage/r18-b.html
Because your car is actually insulated from that noise. Look at every car review ever and there is a section about noise isolation.
Furthermore the sound is also dependent on the length of exhaust - your average car exhausts is longer than a whole bike and for example previously mentioned BMWs wriggle it around the whole engine back and forth just for that reason. This comes at the price of weight and thus handling/fuel efficiency and actual pollution.
With motorcycles, it's a choice, but loud bikes are tied very closely to perceived power and manliness for some riders, plus the whole patently-bullshit POV of "loud pipes save lives." Honestly, it's MOSTLY Harley riders, at least in the US.
I have a motorcycle. It's louder than a car is, but it's not obnoxiously loud at all. You can't hear it from inside YOUR car, for example. Further, I can have a conversation with someone without turning the bike off. MOST motorcycles are like this, in fact. But the loud assholes kinda ruin the overall reputation for everyone.