Apple and Google are changing the way they rank apps in their markets. Although the exact formulas are kept secret, there is talk and news that they are moving away from basing rankings on downloads and now using a formula based on the "sticky-ness" of apps.
The sticky formula is based on the ratio daily active users to monthly active users. So just getting users to download an app no longer gets a high rating. Users need to actually use an app to move it up in the ratings. Seems to make sense. After all, they are called "users" not "downloaders."