Why are Schumacher utterly incapable of keeping parts in stock???

[Cassp0nk]

Seriously, everytime I try to order from them half the items are not available in stock, and when I do place an order for items that show as in stock, by the time they ship they aren't in stock and they dump them out of my order without telling me so I have to do it again and get hit for postage again.

How can they manage their inventory so incompetently?