It is not "just a matter of uploading the APK file". It is also the matter of the vast majority of Android devices blocking apps that aren't downloaded directly from the Play Store, and the user having to go into their settings to allow installing apps from unknown sources, which is a safety measure Android phones have in place to prevent installing harmful apps. I'm aware my apps aren't harmful, but also that some users might not appreciate having to open their phone up to potential harm to install my app from the Internet when they can just purchase it from the Google Play Store, hence why I don't normally upload APKs.
"whatever, i guess i might just end up not playing the others. " Ok. Take care 😁