@Richard A Rudel Jr: I think it is more because you can't actually deliver. You can't sell abstract concepts and the buyer could just claim that he never got the parcel in the end creating more trouble while giving no profit.
@Petros Kavaliotis: Yeah, that finally found a formula that works AKA being Hearthstone's more hardcore nephew. And I mean that as a positive. Protip: use the code 'PlayRavnica' to get three packs of the latest expansion, Guild of Ravnica, free.
I logged in specifically to point out that selling your Soul on EBay is explicitly forbidden by their Terms of Service. (I'm not joking, they actually removed an auction and banned someone for it.)