This is an easy and unfair target. Procurers are on a hiding to nothing.
Economic Order Quantity theory is in Module 101 of any logistics/purchasing course. Do not instruct the supplier to build a batch of quantity 1. Transaction expense will result in the £1,000 nut or bolt. But do not buy a life-of-type spares package...until any urge to modify the kit has lapsed. So the hapless buyer orders a couple of year's usage...and the usage rate changes, such as to zero - see Harrier/Nimrod sudden out-of-service.
Excess stock is always better than nil stock.