Shoes get worn, they get dirty and sometimes the user just neglects them all together. Why put a dark, smelly, oily substance on them that makes them streaked and smudged?
Leave the mess to itself for a bit and start to rub and buff the polish into the shoe. Stay out of the shoes for a bit and let them rest. Give them the treatment they've been neglected as you've taken them along on your travels. When it's time to rest and polish a good pair of shoes back up, take time and take care to do it well.
Some people only get one good pair of shoes and most of those people will make those shoes last for a long time.