Random Question: Why doesn't Apple do clean uninstalls once you remove an app? Every time I re-add Uber (I usually delete it since I live in Austin and it's us

Random Question: Why doesn't Apple do clean uninstalls once you remove an app? Every time I re-add Uber (I usually delete it since I live in Austin and it's useless... but then when I travel I re-add it when I want a ride) it already has my account and password saved. I'd be a lot happier if it did a clean install. Not just Uber, but every app... any idea how I can do a true clean uninstall when I remove an app from my iPhone?