Today the default policies of software are set by the company who made the software.
They have thought through this way more than you.
Their incentives also aren't aligned with yours.
Also, even if you did think about the policies, there are no levers to tweak, it's take it or leave it.
As a user, you know you're doing it wrong by leaving all the doors and windows open and you should carefully set policies by picking which apps to use.
But ain't nobody got time for that, especially in a world so hostile to user control.