Why does no one wash in the movies?

I'm talking survival / disaster / post apocalypse movies.
To star in them you need ragged dirty clothing, dirty faces and hands, and long straggly hair.
And that's just the men!

Once upon a moon I was living on the streets so the opportunity to practice for a movie role as above was easy. It is dead easy to 'let yourself go', but it is also just as easy to keep yourself squared away and clean. The plus is being clean helps to keep you healthy.