How are you saying it should work? Isn’t it pretty much standard that for a crime to be prosecuted, the victim needs to report it, and cooperate with police as part of their investigation?
(Also, ‘press charges’ does not imply suing someone. Also, citizens don’t press charges; the prosecutor presses charges; the ‘Do you want to press charges?’ question you hear sometimes is really just a shorthand for ‘If we press charges, will you cooperate with our investigation and provide us with the necessary information we need to do that, or would we be wasting our time?’ It’s possible that this works differently in the UK (I’m in the US), but I don’t believe it does. If I’m wrong, I’d be happy to be corrected.)