Well, to start with, like most companies, they operate on a "Just in Time" model.
If you invest 2 million in inventory, that's 2 million you don't have available for other purposes.
If you knew anything about supply chain, you'd know terms like "Lean" and "Just In Time". A part gathering dust on a shelf is wasted money.
The company I work for is particularly vulnerable because we are "Engineer to Order". We make a proposal, many of our systems are customized to what the client needs, and it's usually hashed out for a year before it's officially approved.
So we spec out a project using Widget A. Except that the customer likes our design, but they want Widget B in there instead. Now, if we bought Widget A on spec, we'd have a widget we can't use, and we still have to buy Widget B after Cheeto Hitler slapped a 50% tariff on it because the country he made in sad something he didn't like.
This is no way to do business.