It's an overused trope and it's usually handled badly so it doesn't make much sense most of the time
But I read somewhere that for some victims it's a way for them to reclaim their body and feel like they're still "worthy" desirable and huma it's a feeling hard to explain
ive always wondered what the deal was with that trope. its odd how in manga with the trope in it they think that sex after assult makes it better