The trick here is to make auctions seem _fair_. Every economist loves the idea of an auction because it is inherently more fair to sell a good at the price convergence of what someone is willing to pay with the scarcity of the object. The problem is that it often leaves all of the buyers unhappy. Either you got outbid and are annoyed that you need to keep looking for that good, or you won the auction and potentially feel buyers remorse that you overpaid for that good.

I think the problem here is that Ebay doesn't give any metrics on how frequent an item comes to market, nor does it give any pricing history for how much an object typically sells for. Instead of tackling those problems, they just opted for the "buy it now" button.