The sound of the wind in the helmet is still louder. So even if you drive an electric bike, you are prone to deafness (after your theory)? Now what? Forbid helmets? Or wind? Driving bikes at all?
No. You are missing every point.
Perceived noise, at the rider / driver's ear, is a combination of engine, tire and air stream noise. Air stream noise is not transmitted to listeners in the environment, because it's a skin effect, but is only perceived by the driver / rider.
Helmets, like any barrier, will attenuate sound levels at the position of the ear. Helmets create their own skin effect air stream noise.
The point I was making is that the USA mandated max noise level, of 84dB at 50 feet, if it was coming solely from exhaust noise, would translate to the much higher level of 115 dB at 4 feet from the exhaust outlet, where the rider's ear is.
Noise levels from road noise at highway speeds will be well below this, probably less than 105db. Noise levels in the cabin of a car at highway speeds have been measured at around 70 -80dB. Here's a bunch of measurements of different cars:
https://alexonautos.com/cabin-noise/ A typical car reduces noise levels with the windows closed by about 6 dB vs with the windows open.
there is no study that proves the contrary. So we are back to have to think for ourselves. And even a baby knows, that loud sound catches attention.
The study from Association for the Development of Motorcycling in Romania, in conjunction with the Department of Road Vehicles at the Polytechnic University of Bucharest does specifically conclude that motorists in enclosed cars will not hear a motorcycle overtaking from behind, until the motorcycle is within 10 meters. Only preliminary results of this study have been published to date.
Noise abatement laws are seeking to protect others from an individual vehicles excessive noise, not to protect the rider / driver from his own foolishness. I think that besides subjecting a rider to legal prosecution, and possibly assault from other, very annoyed, motorists, constant loud noise has been shown to dull the senses, have negative health effects, and it renders the rider effectively deaf while underway.
I don't expect to convince you. As you say, even a baby knows what it knows. I am certainly willing to agree that "Loud Pipes scare small children"