Some people think it sounds cool.
Some people think it sounds extremely annoying.
Either way it is possible for a lot of these cars to sound quiet during an inspection.
There has been talk about a labelling similar to environmental zones (which means older, dirty exhaust cars can't drive in cities) as well, meaning loud cars would not be allowed in cities.
Edit: oh, and everything louder than 72db, 0.5m from the exhaust at a 45degree offset, is already forbidden for cars iirc.
In my younger days, I had a heavily modified car that was no problem to get to pass, despite numerous possible non-compliance items.
I'm familiar with the measuring method for motorcycles, which basically means that a powerful enough motorcycle will be very quiet when tested because it will be running at very low RPMs (the standard is 3rd gear at 50 Km/h – on my bike that's around 1500-2000 RPM out of 10000).
The noise issue is with people flooring it just to stop at the next light 200 m down the road. And also badly tuned exhausts that pop like crazy.
I'm actually wondering if this hasn't become a fashion for some reason, since I hear more and more cars make that noise. And those cars look pretty expensive, so I don't think they have aftermarket exhausts, if only because changing it is a bit more involved than on motorcycles, and pretty much all newish-looking "fast" cars seem to make that noise.
But I agree, in Paris at least, loud motorcycles are more of a nuisance than cars, if only because there's more of them. Cars do tend to get on my nerves on weekends, though.
Where can I learn about this?
Motorcycles in particular have the danger that if a driver in a vehicle doesn't see them, they can get ran over. Being smaller, they have a tendency to easily hide in blind spots or just not be noticed at all because the driver is expecting another large vehicle.
So many motorcycle riders use flashing headlights and loud pipes to announce their presence.