eBay is competing with Amazon, wants all the B2C business it can get. Private sellers have found that bidding wars don't happen that often any more, if you list low that may be a price you're stuck with. Sniping software has made an impact, I do zero live bids anymore, it's all about the last 6 seconds and pre-programmed bids. Bottom-line, eBay has gotten too big. 30+K employees is alot of mouths to feed, it means your business model has to be more of an immediate transaction marketplace, less of an auction house, less fun.
Private auction sellers have lost ground, no doubt. Lots of risk, and much less upside.