Not having the ability to relist an auction makes using them almost obsolete. I can't imagine a member taking the time to create a Ad/Auction only to find out that the time they spent writing a cool, intriguing descriiption, adding in their personal photos of whatever item they are trying to sell, etc. only to loose all that data 3 days later simply because the auction didn't complete successfully the first time around. The notion that auction data is more temporary than an ad data simply isn't logical, and sounds more like a way to rationalize the current functionality.
I can certainly see running a cleanup job that removes ads and auctions that have either expired or ended after a certain period of time, but I would never expect it to be immediate, nor disallowing the user to "restart" their auction. Either way, there must be some way to allow the user to propagate an auction forward to a new "run" if it wasn't successful the first time and not have to re-enter all that data.
Please look into this issue further and see if there is any way to allow a user to relist an auction.