There’s no technical reason why your phone couldn’t do what you describe. But the goal here isn’t to maximize security or privacy, it’s to maximize convenience

There’s no technical reason why your phone couldn’t do what you describe. But the goal here isn’t to maximize security or privacy, it’s to maximize convenience for the sort of person who already uses the same weak password everywhere for the sake of convenience. Plugging in their phone with a wire is too much to ask.