Steps to reproduce:
1. Open Standard Assets example project or import Cross Platform Input package
2. Switch to Android platform
3. Enable Mobile Input by clicking on menu Mobile Input -> Enable.
4. Build the project to Android device
5. Load CharacterFirstPerson scene
6. Connect mouse or joystick to the Android device
7. Try moving around using latter input device. It will not be possible, as MobileInput.cs script forwards only virtual axes to CrossPlatformInputManager. Appropriate behaviour would be to allow both, virtual and physical Inputs.
If app was build with Mobile Input disabled, external input devices would have worked.