I wonder how much this is due to the "chilling effect" of eBay being lukewarm to sometimes mildly positive to the idea of using BTC. i.e. just receptive enough to put off anyone thinking about serious effort/investment into a crypto-eBay, because if eBay "switches on" BTC payment, it's game over.

So, solution to this is either to get eBay to stop being a cocktease and actually take it, OR somehow get them to be extremely antagonistic toward BTC, so people stop waiting for them.