My town is very bike friendly, and my 4 mile commute to work is 90% dedicated bike roads, but I still wouldn't bike without the ability to adequately hear things around me. Every once in awhile I come upon a cyclist with headphones or ear buds, riding in the center of the lane, and when they fail to hear my call to them that I'm on their left, I pass them in the available space and they almost always end up getting spooked. Same thing with runners and headphones.