Also why bother releasing a plain old APK when someone can use apkmirror to grab it manually. Though at least adding an APK is relatively easy.
And if you are releasing the app manually you need some handling for updates (or informing users to install an update on their own). At least in Google Play users tend to stay relatively up to date. Otherwise any time someone reaches out about an issue you’ll be more likely to find them on older versions, wasting a bit of your time.