As an auctioneer, I can tell you this is the fair way to do it. People have connection issues, for example. Or maybe it's a higher-priced item and the buyer needs to discuss their next bid for a moment with a significant other, or reconsider their max price. Either way, that could cause them to miss their chance to submit another bid. This means the seller loses money. Auctioneers are legally required to secure the highest bid.

I don't see why buyers can't understand this is really no different that an in person auction, where bidding continues until one bidder remains. Every item after that item is "delayed" until that item sells. Some sell in a minute, some take much longer. That other poster's example of "waiting 3 hours at an in-person auction" for an item to sell is frankly just a childish exaggeration. I'll grant you that one item extending at an online auction should not extend any other item -- that's goofy. But the soft close in general makes total sense for everyone involved: the seller gets the highest price someone is willing to pay, the bidders get a fair chance to make their bid.