But there is a separate argument. Why do we put so much effort into trying to increase the teaching of physics to people, it goes, when there are no jobs for those people once they finish?
This is a problem. In a traditional sense (ie, academia, government labs and highly skilled industry R&D), there simply aren't enough jobs for even those relatively few physics PhDs that we produce. But this isn't the whole story.
Physics bachelors tend to have a much better time of finding a job than physics PhDs. They're generally less specialized and therefore wind up in any number of various scientific and technical fields, whereas a physics PhD graduate has really chosen to do something quite specific as a career.
But even this isn't the whole story.
Here's really where the "supply and demand" argument breaks down. Physics outreach isn't about producing more career physicists. It's about producing a scientifically literate populace (who can then go on to train in whatever else they choose). I want you to know physics, not because I want there to be more physicists, but because knowing physics is important in its own right.
Sure, I myself am searching for a permanent job, and I wish there wasn't so much competition. A colleague of mine just recently applied to a tenure-track faculty job only to be told that there were over 200 applicants. And I've argued before that it sometimes seems that certain people graduating with PhDs didn't deserve them (this is a whole separate problem!), implicitly indicating that the system which creates these PhD researchers is broken. But does that mean I would argue against teaching as much physics to as many people as possible whenever possible? Never.
Physics is more important than the physicists it employs (or doesn't employ, as the case may be).
*Of this ~1300, approximately 3 to 4% are in Applied Physics such as mine is, and roughly 12% are women. This makes me roughly "one in 65 million." I just found that interesting.