(come in go away mat, buy here)
It doesn't matter whether or not you wear shoes in the house, they're still coming in along with all the lovely things that have been picked up from the street. And you don't want that in your home and/or closet... Your choice; spend $3 at your local hardware store, $100 for a custom one, or any amount in between.
It's a no brainer, seriously - if you don't have one, get one now!!