Cats don’t usually need to be bathed because they groom themselves. They do need to be brushed and some long hair breeds may need to have their fur trimmed. If a cat can’t groom himself properly due to an illness or other reason, a little help is necessary. Make sure there is not a medical reason for their lack of grooming by taking him to the Vet.
Sometimes cats are a little chubby and can’t reach all the places he used to. I had a long haired cat that couldn’t reach around her neck. I had to keep brushing her and cutting out the mats around her neck.