Auction question

When you outbid someone with less than one minute left on the auction, why does it add 10 minutes to the auction? This seems a bit strange to me. I have never seen an auction work like this. :S

I know some die-hard bidders who use a bidding engine to monitor auctions. Essentially a software that places marginally higher bids in the last seconds of an auction. If you add 10 minutes, you take the engines out of the game.

have fun,
dan