Shelf space in their stores is at a premium. They don't carry much which means that shelf space is a huge deal. If your selling out of a product the second you get any stock in, then there is no need to promote it. They will wait till sales slow down and they are not sold out all over to put them back again. Why waste space for something you can't really sell. Shelf space is used for impulse buys... "Hey I just bought a MacBook Pro and Final Cut, what should I edit with it, ooo look a drone!" but if they say that you have to wait, then you say, "Ooo look a camera".