To collect money for something you don't have with backorder as the rationale is introducing complication into what assuredly ought be a very simple transaction, that the customer pays for merchandise that the retailer has and it is shipped to him. Why would anyone tender cash for something that doesn't exist? Why would any retailer take it? At least half the time this is going to mean unnecessary complication, irritation or anger and phone calls.
One popular retailer has backordering as a customary procedure, in part I think to avoid the cost for software that tracks inventory and permits sales only for stock that is available, which given the profits of an organization of this size, is bad business in the name of greed. In addition I also accord them the greed that takes the money first without regard to the irritation and frustration on both sides which such stupidity will cause.