I'm sure it varies somewhat from company to company, but the general ethos was to reduce warehousing to an absolute minimum. From a corporate finance perspective, this has a bunch of benefits. Excess inventory is effectively unproductive capital. Additionally, it's costly to store and is subject to theft and damage as well. A lot of the focus on JIT came out of post-war Japan where capital was scarce and this was done out of necessity.

In some cases, an incredibly aggressive supply chain and payment schedule can actually create financing for a company. Aswath Damodaran's corporate finance class mentions one of the major alkaline battery producers as an example. At any point, they only have 2 days worth of production in inventory, and they require payment within ~7 days from clients, while their own suppliers are paid after 30 days. That means at any point, they are holding about 20 days of revenue worth of cash without paying any interest.