I don't necessarily think it gets me more bites but it's definitely a situational tool. For instance, when trying to get through deep grass in cold water, I want a bulky profile. Also, there are just times when the fish are biting and putting that skirt on will get you bigger bites. Another advantage is when that water is dirty, put a skirt on so the fish can see it easier. It's mostly a preference thing but there are times when it does make a difference.
"If people concentrated on the really important things in life, there'd be a shortage of fishing poles." - Doug Larson