Is there any understanding of why dreams have such common "Tropes"?

Your teeth are falling out. You're in a speeding car you can't get under control. You're in a public place with no pants on. You suddenly find yourself back in high school, taking a test you haven't studied at all for.

Why do dreams seem to follow stock premises like these and more, shared among people who have them independently, often even without knowing they're commonplace?

I know dream interpretation is probably pseudoscience, but is there any kind of concrete rationalization or attempt at explaining why these themes are shared across cultures?