well I'm assuming that android has not got trialled is because it's App Store isn't as secure as the iOS one. You can easily get many apps that help you cheat on games on android whereas it's practically unheard off for the iOS App Store.
I'm guessing people could probably get apps to skip the trial pay service and make it seem as if they completed the task when in fact they haven't? That's just a guess I don't actually have a certain answer.