I honestly cannot give a qualified answer, but I will try. Hopefully someone with more knowledge of Android will correct me and I will learn in the process:
On Android, every app runs under a separate UID. This is to ensure any specific app cannot access files written by any other app unless that other app explicitly grants system-wide access. In a world where you expect every program on your device to spy on your data, this is supposed to enhance security. Effectively, this alone makes something like a file browser impossible: on Android, these have access only to files that belong to t