He washes many times a day. He doesn't use soap and water but his tongue. He may eventually begin to smell a little pongy as he ages and finds it harder to reach those stubborn stains.
I have three persians. I groom them a lot because of their long hair, but I never bath them or use anything on them. But they always smell so nice. I had one who was 16 when he died and even though he was so old he smelt good too!
Maybe the environment they live in has a lot to do with it. I mean everyones house has its own smell dont you think?