You only find them in places we seldom go. If we remove them, they are back by the next time we look in the same place. Look, the odds are they are friendly. As you get ready to fall asleep tonight, think of those little dustbunnies under the bed, and you decide which explanation makes sense to you. The point is this.
Websites tend to accumulate files.
Moving unused files to your trashcan directory keeps them out of the way. This will make it easier for you to find your real information, and also make your site faster. The speed impact is especially great if you have a search engine on your site. The easy way to a consistent site. Yes, there is an easy way to keep your site from ending up with sixteen personalities like Sybil.