There’s no reasoning “why” when it comes to sexual selection. It just is. You find attractive what you are conditioned to find attractive. Birds are turned on by brightly colored feathers. Baboons love an ass that looks like a 40 pound hemorrhoid to me. For all we know, mole rats find Norway rats to be disgustingly hairy. I’m sure that dogs are puzzled by the human fixation on fatty mammary glands.
Do zombies have hair? Or, rather, do zombies grow hair? Or is the hair they have just left over pre-zombie hair. Can’t find a wiki page for answer.