Tons of animals don't give a crap if they smell, and why should they: they're animals. They're supposed to not give a crap. Occasionally a dog will clean himself, and cats and rodents clean often, but I'm pretty sure that's less about smell and more about looking pretty (goddamn animal vanity), because they still smell afterwards.
Most humans do care if they smell, and if they don't, they're assholes. The people who don't give crap if they smell are the same people who don't give crap if they cut you off in traffic, accidentally trip you, or plunge the economy in the shitter while giving themselves a raise. It's just common courtesy to make sure you don't smell like a Limburger cheese factory everyday. But if an animal smells bad, they're being a typical animal.
(flickr photo Dirty and Happy by YouDooAllous; http://www.flickr.com/photos/youdooallous/2630128910/)