The well groomed individual gives the signal that someone is caring for him, almost like the protective signals given by children - no glandular odors, smooth face, and fresh breath. It has become a posture of social facilitation - of gentlemanliness. These are the signals used as personality clues in psychiatry. A person who has completely let himself go to seed, physically, is someone who has lost his social state - in his own evaluation he has no one below him in the rank order and therefore has no social front to maintain. A major taboo in most human societies is dirt.
Dirt is bad.
We rationalize the social stigma of dirt as unsanitary. This is essentially a myth. Coal dust, soil particles, and petroleum grease are for the most part free of pathogens. Dirtiness is the main thing which around the world separates castes and classes. Big feet in a woman are considered ugly, more masculine.