I think only you can answer those questions because the answers are are your own personal reasons. It might be some sort of sense of disbelief that it even happened. I'm thinking too of war survivors who keep things related to war injuries; I think it's a reminder that they feel lucky to have survived.

Possibly you have a good healthy outlook about the assault and know that the clothes may be a reminder, but they weren't the cause; they just happened to be there.

I think it's only important to get rid of them if that's what you want to do.