Its not like, customer demands and vendors supply. Both "sides" have both, supply and demand. Customer demands the product and supplys the money. Vendor supplys the product and demands the money. When both "sides" get their supply and demand fulfilled, all is rosy and peachy. When they dont...customer doesnt get the product and keeps the money. Vendor supplys the product and doesnt get the money. Which for customer means waste (as in "spending for nothing") of time, effort and money on demand. On the other hand, for vendor it means waste of time, effort and money on supply. Thing is, demand is a lot cheaper to produce than the supply. So loss (or potential to lose) is a lot higher for vendors than for customers. Hence the vendor tendency to reduce potential for loses with certain practices. Like in this case, to supply the products for established or well known figure, rather than new or not well known one.