Money. Many Android tablets are full of pirate apps (you just need an APK file). Plus, IOS users are, on average, more willing to pay. It's why some apps are $0.99 on IOS and free with ads on Android.
Personally, despite you just needing to install an APK, I don't know a single Android-user running anything not installed from the Play store.
Obviously the XDA crowd is different, but they are a clear minority, and I know almost nobody IRL who goes that route.
>More apps than Android: Apple's App Store has more than 425,000 apps. The Android Market has 200,000. In May, Google (GOOG) announced its 4.5 billionth app download, compared with Apple's 15 billion as of July 7.
Where do you read that iOS users were paying more than Android users in that article?