The reason there are no bicycles in zombie films is because the second you put a motherfucker on a bike they start to smile. And you just can’t have that shit in a film where your heroes are struggling for survival in a crumbling dystopian apocalyptic hellscape dealing with the bleak pointlessness of the modern human condition. Bicycles are intrinsically hopeful things, and except for the very end zombie movies are generally all about a setting of hopelessness and despair.