Basically as everyone else has said, AV programs for Android are a solution in search of a problem. I know it's this huge story when someone finds a potentially malicious Android app, but there've been what... Maybe a dozen such stories? And how many apps are there on the Play store? Calling it a drop in the bucket is to vastly overstate the situation.
Maybe... Someday... In the distant future, this might change, but right now it's just companies looking to play off of people's fear and ignorance to sell them useless products.