For example. Reasoning is the same that allows you to listen to the radio: as long as you can hear car horns and emergency vehicles, you can listen to whatever at whatever volume. But you can be found more at fault if you crash into something, in certain cases.

Anyway, now you know.

Its dangerous not to wear hearing protection on motorcycles over like 60mph for long rides and much shorter rides if you go slower.

I'm in Australia and had no issues using a full headset. Using it because car speakers didn't work, according to a cop it's only an issue if it's noise cancelling.