Some people claim similar things about rape and try to use that as evidence showing that the accusation is false ("she could just have kept her legs together"). It's a bit disgusting.

And there are good reasons for that, it's to protect innocent people from false accusations. It looks like he'd be well within his rights to sue over this allegation.

Also bad reasons such as saving face or reducing workload for police officers.

Do you really think that's the case all but a small minority of the time?

Most officers go into the job for altruistic reasons and I bet they'd rather help convict a rapist than to write a speeding ticket.