I would think it not to be on the part of ebay.
It is probably as a result of sellers that have experienced losses and are trying to cover themselves.
If this were an ebay requirement, I think you would see it on all auctions.

Get ready Phyllis, I'm sending you something special this evening.
Requires no assembly nor do you need a 10 year old [ Though it might help]
Merely requires..... Warm clothes and a shovel