Ok, when I drive with my headphones at a volume that I can still hear my bicycle chain rattling, I'm not automatically worse than someone with their car radio so loud I can hear it 100m behind them. So I don't think laws that prohibit headphones specifically are necessary, let it be managed by the same laws that bind drivers to keep their radios at a sane level.

But point taken that some governments classify any headphones as distracting, I suspect because one can generally identify radios that are too loud, headphones that are too loud are harder for police to prove.