Comment by kylecordes

Auction site design where most every transaction is a very material amount of money for buyer and seller probably have different trade-offs from something like eBay where most items are rounding errors compared to the income or wealth of the participants.

For example, think about "sniping" from the seller side. Sellers are rightly concerned about any wrinkle of the bidding process that might leave money on the table. Automatically extending the time so that every potential buyer has time to "answer" a new bid soothes the concern that buyers were willing to pay higher, but they didn't have the technological prowess to post their bid in the last 0.3 seconds.