That very much depends on the cat and the type of coat they have. Some coat types have a tendency to get very compacted and/or matted if they aren't bathed regularly to loosen the shed hair. Some cats are unable to properly self-groom and need regular bathing. Sometimes a cat gets into something really nasty and letting them self-groom could make them very sick.

It is until it isn't.

Everyone should bathe their kitties at least once or twice just so that they know what that is. Then you do not do it again until they are adults covered in the blood of their enemies and tracking it all over the house.