if you're asking earnestly, one of the biggest reasons is that the would-be prosecutor relies on the cooperation of the police department to function. This article covers that and some more:
In some countries it’s possible for civilian lawyers to press criminal charges specifically for situations like this. There’s some gatekeeping by the courts and whatnot to approve the case but it’s pretty reasonable. Also allows victims to “press charges” when the police mysteriously refuse to.
Burden of proof remains the same as for a state-appointed prosecutor. And judges still get similar leeway in sentencing.
Oh totally, theres lots of ways it could be improved. Unfortunately, our courts are also in their pocket for various reasons, and invented whole cloth the concept of qualified immunity. So getting the case to the courts is no guarantee either. Still would be better of course.
I find it so sad, how much of the country was united on this for months, and how little has actually happened in response.
https://fivethirtyeight.com/features/why-its-still-so-rare-f...