This is where big business and friendly dealings between stamp collectors clash, perhaps irreconcilably.
If
ebay wants to be the next
Amazon, and they say that they do, then they can't have buyers not receiving their stuff. Can you imagine if an
Amazon buyer was told by
Amazon or an affiliate, "hey, we mailed it...sorry you didn't get it." They have to guarantee delivery in order to make the experience palatable for new buyers.
That leaves those "hobbyist"
ebay sellers that generally had lower-value items distinctly out in the cold. If a couple of losses put a person off of selling their traditional twenty to fifty items per year, well,
ebay might be fine with that. Us small-timers aren't the future of their business model.