They might not have a controller, they might not like using controller, they might be physically unable to use a controller, regardless not being able to rebind your controls is an extremely valid complaint
Even if they don't have a controller, wasd doesn't make a game unplayable at all. The only possible problem if they have a keyboard is if they don't have arrow keys, which almost every keyboard has.
Edit: How would you be physically unable to use a controller but at the same time be able to use a keyboard??