Could it be the addictive "sound" biases opinions?
I'll speak for myself..
The Kerkers on my ride have Minton's Mikuni baffles. Took a while to figure out how to quieten them down, for my neighbor's sake, yet keep'em loud enough for my liking.
Sport endcaps were loud, 6 inch slashdowns..louder. Then came the fishtails..the right SPL on light throttle, big bark when I pull the wick. So, I'm mindful with my throttle in town.
What has any of this have to do with my safety?
In the city...it would take just as long (maybe even longer) to rev up the motor as it would to hit the horn button for anyone pulling a brainfart in my immediate vicinity.
But lots of boneheads are too happy to pull that throttle so they can be heard in neighborhoods, like the one I live in. Why do they do it? Cause they can.
It pisses me off when some clown whaps the throttle going down my street...cause THERE'S NO NEED! Irritation level's right up there with the sound little 4bangers with a BIG honker of a bottle for exhaust make...they sound like pterodactyl sized hornets

.
Now, the highway is different. Noone to piss off (or warn) but animals...and hell, that don't even work for some of us (buddy had megaphones on his Glide. Didn't matter, elk took him out anyways..)
Sharpening up awareness, anticipation and other skills of the road would go a long ways for our safety, much the same as what Gomo states.
What I'm getting at is...loud pipes are just....loud pipes. More addictive by design. Tagging safety as a byproduct is a claim that's wearing kinda thin
(It's 60F, nothing but blue up above, so...I'm outta here. Getting it while I can

)
My .02