Loud pipes have a couple of significant disadvantages. Most important one is, that they are annoying to non-motorcyclists and contribute to anti-motorcycle opinions in the public.
One other important one is that they require a retune and rejetting of the carbs. A louder pipe, in most cases, has less interior restriction thus requiring a different intake mixture.
The Supertrapps are the loudest ones I know, if used with more than six tuning discs or an open end-plate.
To be understood is the exception
To be misunderstood is the rule.