I don't think it's whether the beds are filled up, I sure many injuries are carelessness, it's how easy is it to avoid it.

Losing weight is insanely hard getting a shot or two is easy. In fact if you had some kid who was speeding, got into a crash, and is now taking up a bed I'd argue that self control for young adults in related to reckless behavior is much more difficult to stop than not getting a vaccine.