Here's my standpoint: I don't want a system where any binary can just read/write all my user files. Prompting me is the most straightforward way to implement this.
Most users already know this behavior from their phones, they aren't all so dumb and reckless. They reject permissions all the time, which we know from statistics. They don't just mindlessly say "YES" to everything, but even if they did, why put everyone at risk, just because most people aren't diligent?