Even though what you describe has, for some reason, become much more common lately, many exhausts are just loud for no good reason. Think Harleys or even the Yamaha TMax with the Akrapovic exhaust. They don't have the "pop-pop-pop" sound related to detonations, but are still absurdly loud.
> There's plenty of motorcyclists who do the same though.
What's funny is that in my neck of the woods, it's motorcycles with bad aftermarket pipes that had been making that noise for a long time. So now, whenever I hear a car making that noise, instead of associating it with some "big mean engine" as their owners probably hope, I associate it with some overworked 600cc.