They say that the current demand and lack of supply isn't sustainable enough to justify the HUGE expense and process of building the facility, the cost and process of being compliant with EPA and other regulations, hiring competent workers, etc, etc.
I can understand that. It seems like a no brainer, but honestly it would be a massive undertaking and would take a ton of money for the initial investment. It might actually be a worthwhile investment, but it's s huge gamble.
Right now, all they have to do is buy, package, and resell. They don't have to mess with hundreds to thousands of employees, the operating costs of a factory, and all the extra BS that goes into owning and operating such s facility.
There's a reason the like 40 some powder facilities that DuPont owned and operated in the US all shut down and went away. The US government I'm sure makes it pretty much not feasible to open up a new facility. Same reasons why so much US manufacturing went overseas.