I work in a building with a board assembly line that sits idle most of the time. They have tried securing outside contract work to fill in the gaps. No takers yet.

The only domestic drivers for board fab and assembly are autmotive and defense. They already have their supply chains running.

Makes sense. Is it that most of the time is spent switching jobs or that there's just not enough jobs going through it?

You're right that automotive and defense make up most of the demand. We also see demand from teams who can't use JLC/PCBway due to the difficulty of cosigning parts outside their catalogue.