Your false equivalence is showing. Race car drivers wear their helmets in their cars.
What I think @
rachel120 was referring to is that riding a bike on the streets and driving a car on the streets are just different modes for the same function. There's no reason listening to music should be any more or less safe on a bike relative to a car. Luxury cars are so soundproofed, drivers may as well have noise-cancelling headphones on.