Agreed.
I've frequently used earphones whilst driving, usually because the truck (44t six axle artic) has no radio or the one that's fitted won't work.
Ok, now the thought of a 44 ton lorry driver wearing headphones is downright
****ing scary.
What happens when you're doing 56mph on a 2 lane dual carraigeway, go to overtake a slow moving van/car/lorry, check your mirrors & blind spot, indicate, move out, and in the time between checking your mirrors and moving out, a biker who was directly behind you in your blind spot is now alongside, and as you've moving into his space in the outside lane, he's got his horn on full blast, only for you to not be able to hear him because you're "drowning out the noise of the refridgeration unit" or tapping along to that song you love, and you keep pulling out, forcing the biker to brake, lock up/hit the central resveration, and go under your wheels, crushing his skill/spine/ribs etc. killing him instantly.

Seriously? I'd have though being in control of a machine that is capable of killing multiple people in the space of a few seconds, you'd know that you need ALL your wits about you and have to rely on ALL your senses. Fair enough, trying to stay awake and alert, but that's a completely different issue, and you shouldn't be driving if you're falling asleep at the wheel.

Headphones ARE different from listening to the radio, they block out more sound, you can't argue that. With loud music you can still hear other things around you, headphones block anywhere from some to all external noise.
And yes deaf people can drive cars, but as someone else said, they compensate with their other sense, and aren't distracted by the music balring in their ears.