If you develop your Android app(s) in a small team without a dedicated QA guy or in a one man show, you have to test the app on your own. Usually developers test the app in the Android simulator with different Android versions and at least on one real device. The fact that Android is available in hundreds of custom configurations on over 200 different devices makes testing a real challenge for small teams. To ensure that your app runs on every device, you would have to buy a lot of hardware and need a lot of space to store all the devices. This waste to much time and is also very expensive.
But this could change now!