I was actually thinking that too, recently. Even if most of the people that have bought cryptos are just holding them, there should be an eshop for those that want to keep their anonymity when they'll pay. I don't understand why ebay does not allow their users to accept bitcoin. (with their own responsibility)
That's the thing, they can't take full responsibility for it, either in terms of security or in terms of applying Bitcoin as a payment model currently. Can't really force them to put something out when they themselves don't really see any advantages in doing so.
Additionally, afaik Ebay fees are mostly on them being a third party middleman between the seller and buyer plus the fees from delivering items from place to place, add that to the additional fees they get for profit, fees would naturally be quite insane, especially if you're buying from someone overseas. I highly doubt crypto could even do something about it, since it isn't the issue of transferring money, but rather the issue of the fees of transferring the items.