[android] Why does the Google Play store say my Android app is incompatible with my own device?

Though there are already quite a few answers, I thought my answer might help some who have exactly the same problem as mine. In my case, the problem is caused by the following permissions added per the suggestion of an ad network:

<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />

The consequence of the above permissions is that the following features are added automatically:

android.hardware.LOCATION
android.hardware.location.GPS
android.hardware.location.NETWORK

The reason is that "Google Play attempts to discover an application's implied feature requirements by examining other elements declared in the manifest file, specifically, elements." Two of my testing devices do not have the above features, so the app became incompatible with them. Removing those permissions solved the problem immediately.