I ride bikes off-road and come across stuck or broken down vehicles occasionally. Always surprises me how precarious driving a 4x4 can be on fairly mild terrain. You need two tracks whilst a bike only needs one. You need vertical clearance between the wheels in both directions. And there is no way to just get off and push a few metres. Trying to navigate between obstructions and zombies on a deteriorating road surface would be challenging. Although I don't fancy changing an inner tube in that world.