How can you say there is no downside for sellers?  Here is the downside for sellers:

I use a courier for postage, as it is MUCH cheaper than any of the ebay postage options.  I have NEVER had a problem with the courier or delivery.  When customer pays, I would receive the money (in paypal ac), book courier for next day pick up, and in the morning parcel is gone on its way, I am paid, ebay is paid.  Now, I have to either 1) pay for courier out of my pension, then wait days till ebay pay me back, or if I cannot afford to use my pension 2), use much more expensive postage options provided by ebay. so for me the system is losing me time and money