Now that you -- an interesting, fun, smart, ambitious person who has a million things to accomplish -- have been assaulted or harassed, you have a choice. You can tuck this Bad Thing away in your brain and keep living your life as normally as possible, or you can step into the second part of the nightmare of assault: the part where you describe the experience over and over again in front of people who may or may not believe you, who might actually be paid to tear you to shreds in public, and who can destroy every dream or ambition you've ever had for yourself. Oh, and if you choose to step forward, your name and your assailant's name will be linked forever and ever, even after you die. When people think of you, they'll also think of him. That's what you're signing up for when you come forward.
The best-case scenario is that everyone believes you, no one blames you for what happened, and no one thinks your pain is too insignificant for discussion if you weren't raped. The worst-case scenario is that you end up on national television telling old men how your boss used to describe porn to you and once asked you "Who has put a pubic hair on my Coke?" before he was placed on the Supreme Court.
Whether we're talking about persistent unwanted advances in the workplace or rape, it takes a Batman-level sense of justice and ovaries of steel to walk into the hellscape of naming names. A lot of women (and kids and men) coldly and carefully look at the path ahead of them, then say "Nope!" and just keep living their lives as best they can.
Until they realize that someone else might get hurt.
I'm not a therapist or an expert or a historian of sexual misconduct, but I suspect that the nebulous concept of "justice" is rarely what compels a victim to come forward. The harm is done and will never be repaired. I think victims come forward when the fear of this same assault or harassment happening to other people becomes so gripping that they can't handle it anymore and they have to say something. It's the love of other humans, future unknowable victims, which fuels a woman's fight through rape kits and police interviews and HR hearings and the courtroom glares of their assailant's loved ones. And only the bravest, most selfless heroes can do it.