I think the reason why mental health is more public these days is because it wasn't talked about and addressed.

To extend you physical injury analogy: yes, people get physically injured. People break legs, and because of the focus and progress on physical injuries, they wear a cast for a few weeks, and then - for all practical intents and purposes - the injury never happened.

Because the same attention wasn't applied to mental health, I think people realised they were surrounded by the equivalent of people dragging themselves around on the ground because of a broken leg a decade ago that never got fixed. Why would anyone do that? Either because they don't know about the treatment, or because they live in an environment where the idea of getting treatment is seen as a bad or weak or shameful thing.

> Why is it so implausible to say that practically everyone can expect to eventually have to deal with at least one significant mental injury, too?

Just like we expect to walk down the street and see the occasional person with a plaster or bandage to handle a physical injury, if you accept we all have mental injuries, why do you expect to see them handled any more privately than physical ones?