The behavior you're describing is expected on Android.
Message Center is integrated at a device level. This means, any messages in the Message Center are tied to the device, not the user.
The way we handle this on iOS is by associating the Message Center to the Channel Id on iOS. We store records of the Channel Id in the iOS keychain, which is generally retained from uninstall to reinstall. So, you would expect your messages to stay on iOS.
However, Android has no such feature. As a result, the Channel Id and any other information about that app or device is cleared on an uninstall. When you reinstall, it's as if you were installing the app for the first time resulting in a new Message Center and new Channel Id.