Same difference. The point is, when the waypoint has been passed, it is no longer a waypoint and disappears. Some of us prefer it that way.
EDIT: It's only redundant if you enter the destination twice. Who does that other than the OP? As I said, you can mitigate this issue completely by rearranging your instruments. I think more map space is more valuable than a "redundant" instrument or an instrument with NO information.
EDIT2: And just to beat a dead horse, if you're flying around with no flight plan, the Final, Dist, ETE, and XTE instruments also disappear as they should. I guess someone could put in a false destination or their departure airport as destination for these instruments to persist, but why?