'Just In Time' stocking has been the mantra in the supply industry for years. It was the begining of a day dream that ware houses that had too much un-usable stock laying around for years. (Which in thier minds is money in the bank that does not collect interest, and becomes obsolete...)
So the idea was that if an end user needed something, they could order it, and have it "Just in time" for when they would need it. That way a supply house would not have a case of (24) 3 gang over-sized brown plates collecting dust on the shelf for years when that 24X1.98 ($47.52) could be collecting interest in a bank. On top of that... If you consider the cost of urban and sub-urban real estate, that box could cost more to store per month as .5 cu/ft of shelf space also needs to be paid for. For them, it may cost less to ship and handle a small item like that than it would in storage of stagnate capitol.
The problem lays in what the end-user, and the supply chain see as "Just in time". Lead time for a 3 gang plate is much more, because the supplier figures you can wait a few days for some un-consiquential item like that. On the other-hand, if you need a high dollar transformer and they know you can not wait for it (or go somewhere else) would be shipped over-night from some low dollar sq/ft warehouse in deep space special just for you. A low dollar item of low importance may have to come from a warehouse in the Dagoba Galaxy...
FYI I was a warehouse and distribution foreman for Mass General Hospital before I was an Electrician. $3.5M of material inventory, and when they needed it, they needed it yesterday... Another $3M handled each month that was too expensive to store in stock... Labor is cheap when floor space is going for $130+sq/ft.