This is often because Yelp is a great resource for travelers, and people use Yelp to find local spots when they’re outside of their local area.
However, users can also select which information they'd like to share with businesses. For example, a user may share their hometown location but not where he or she is currently living. So, the Activity Feed may display that someone from a different city or state has viewed your business, but that user may actually be residing in your area.