Cats who spend most of their time outside typically whiff more than indoor cats, if only because they spend more of their waking hours hunting and avoiding being hunted. Those who live in grimy environments may avoid grooming for their own good.

My Dad served in the Royal Navy during the war. His first ship, a small, rather nasty old destroyer called HMS Wrestler, carried a cat known as Bombhead (pronounced Bomm'ead) who spent much of his time hunting rats in the engineering spaces and thus ended up caked with toxic filth. As Bombhead was too wise to wash himself, the Coxswain assigned his care to the men whose part of ship was the quarterdeck, i.e., the signallers and radarmen, including my Dad. Bombhead was bathed (in a bucket, with Lifebuoy soap) each Friday and inspected, along with the rest of the ship and her company, by the Captain each Saturday morning.