"Loud pipes save lives" is nonsense. When a driver is concentrated on visual stimuli, has his windows up and music playing, there are no pipes loud enough to make him notice me.
Why loud pipes then? Because it's so much fun to open the throttle wide and hear and feel the roar vibrating through the bike and myself! Makes me feel like I'm riding a rocket into space.
Do I do that in towns? Very rarely. I mostly try obeying speed limit with calm hand on the throttle and reasonable engine speed and shooting off when leaving a town. I'm super noise-conscious when riding after dark. I also don't rev on red lights just for the hell of it. I live on both sides of this problem, as a city dweller i hate being woken by noise, but it's more often some doofus in a knocking diesel car letting the engine idle for 20 minutes as he picks up his friends at 11 pm. I guess cars like that wouldn't be punishable, because they are not tuned to make noise. And when I hear the whine of a motorbike from the hills on the outskirts, it just makes me smile and plan a next ride.
To sum up: yes, loud pipes can be obnoxious, but it depends on the driver. If they get banned, people like me will lose a part of their hobby and noisemakers will find another way to be obnoxious (burnouts? screechy braking? loud music?)