"Other app stores" do exist, but Google went to great lengths to destroy them. Publishing clients for alternative stores in Google Play/Android Market have been

"Other app stores" do exist, but Google went to great lengths to destroy them. Publishing clients for alternative stores in Google Play/Android Market have been prohibited by Google's ToS for years (don't know if it is still prohibited). The "allow alternative app sources" checkbox (unchecked by default!) has been deterring users from installing from non-Google sources till Android 8. It still exists, but Google have ruled, that third-party marketplace apps are better than malware-riddled piracy websites, so Android 8+ allows to whitelist specific marketplace apps while still keeping the checkbox unchecked. And let's not forget about Google's war to banish alternatives to their services from Android devices, while using their own Google Services packages as leverage. Google's overall approach to building it's walled garden is not much different from Apple's. They give some fake "choice", because they know, that tech-illiterate consumers won't be able to make use of alternative options.