I'm a industrial engineer and have worked at 4 factories and am familiar with far more. I don't know of a single company where production employees are paid salary.
I talked with a production employee about it when starting my current job. They said "man I could never work a salaried job. I'd get so frustrated with it".
There are pros and cons to the typical US salary structure.
* If the company gets too aggressive in the expectation of hours worked, people just leave since they're not getting overtime pay.
* I also have flexibility to start/end my day when I want within reason
* I never have to take time off for doctors visits
* I don't have a micro manager for a boss, so if I work 35 hours one week and 45 the next, nobody cares.
In the US, hourly employees get at least 1.5x pay for working beyond 40 hours. It's often cheaper to pay for overtime than expand the workforce, so some companies hand out OT like candy at a parade. An employee can double their pay by working 66 hours compared to just 40.
There are often also shift differentials. They might be a couple extra dollars/hour for nights and a couple extra for weekends.
Most salaried employees are "salary exempt" and are typically not paid overtime.
I believe there's no way in California for the kind of worker on Tesla's factory floor to be considered exempt, so he would almost certainly be getting overtime even if salaried. You could easily meet the 2x minimum wage annualized pay exemption, but the "administrative/executive" exemption would be an absurd stretch. A few people might meet professional exemption but probably not most of the workers, and the ones that do are likely already salaried. (I'm not a lawyer, particularly not an employment lawyer in California, though.)
> I don't see how any of that is relevant to whether one has salary or not?
I suppose it's not specific to salary, more to the type of work. In the US with production workers, a salary would be quite unusual. I have friends working at many companies and have never heard of the production employees being salaried.
> * I also have flexibility to start/end my day when I want within reason
Generally production employees work specific shifts with specified start and end times. Showing up 15 minutes late yields a verbal warning, 1 point on a discipline tree, etc. This can happen with salary positions as well, but I can't say I've ever seen it. It's more a "get your work done" attitude than anything.
> * I never have to take time off for doctors visits
I should have said "If I get sick, my paycheck isn't any smaller because I had to go to the doctor or take 3 days off."