I love Android but Google don't believe in file management as they want Android to be user friendly, personally I think this is ridiculous as I have memory management OCD and a file explorer is important to me especially on a device with such limited storage.
If uninstalled apps didn't leave folders behind and app caches were cleaned by the apps themselves then maybe Android could be used without a file manager but for now I will go against Google, use a file manager/explorer myself and suggest to others they do the same, it's the only way to keep a limit storage device like the Nexus 7 clear of unwanted storage hogging clutter.