It bothers me to no end that rapiers get sheathed on your back.
So I am not the only one 😄 It would be nice if our character could wear it at the hip.
I can only guess that it's a clipping issue, but IMO it'd still look better on your hip than on your back. Like, entire armor sets have clipping issues by themselves so I don't think it'd be a big deal if rapiers/maces/longswords clipped through characters' arms a bit.