Part of it is that prosecutors don't want to give the woman an incentive to hold on to her story to the bitter end. I would go with no prosecution if she voluntarily recants, but prosecute if evidence shows she lied.
I read one article that claimed that rape accusations essentially come down to a “he said—she said” scenario, because the rape kit only shows that an act took place, not that it was rape. That isn’t quite true. During rape, a woman is uncooperative, which leads to certain stereotypical injuries. I’d say that the absence of those injuries should make an alleged rape that much harder to prosecute.
Forcible rape where the woman is actively struggling against the rapist should show signs of that struggle.
Rape where the rapist secures cooperation by threatening injury or death if she does not actively cooperate, might not show signs of force.
Except that there really are women who enjoy rough sex and being overpowered.
Signs of a struggle therefore cannot mean that intercourse was necessarily not consensual.
Our present legal system presumes the validity of the accusation and the guilt of the accused in multiple ways.
Most notably, we shield the identity of the “victim,” and plaster that of the accused all over the media, usually associated with a handcuffed perp walk for the cameras.
In fact, the routine use of the word victim prejudges that a crime actually occurred, although not necessarily that the accused is the perpetrator.
The sexual history of the accuser is also in many states shielded, despite the fact that it may often be highly relevant to the defense. I’m not sure, but I don’t think the history of the accused is shielded in the same way.