Overt rock references aside, have you ever noticed how bicycles are absent in the games, despite their usefulness?
They're extremely efficient, able to convert energy normally used for walking into speeds that are several times faster than that of a walking human, they're easy to repair and maintain, allow for transporting cargo...
Most of all, they're faster and allow one to cover much more terrain. I'm wondering why hasn't anyone in the Fallout universe started to use them.