The ancient Egyptians had pyramids. The ancient Romans had aqueducts. The bloodthirsty Vikings had longships. Some historical civilizations are so well-known, almost anyone with even a passing interest in the past would be able to fire off their basic backstory and list of traits.
In fact, someone with only casual experience in history may think that (because of the intense focus that some civilizations garner), the history of the world is made up of only a few powerful empires, and that everyone else is unimportant.
Nothing, of course, could be further from the truth. Oftentimes, a civilization will be incredibly influential and important, but won’t receive a lot of discussion. Normally, this is because there’s nothing left to discuss.
These vanished ancient societies leave large gaps in our understanding. History is, at best, an inexact science, and can best be imagined as a book with several pages missing. Some of the lost cultures and mysterious historical civilizations that we know the least about probably have some of the most interesting stories to tell. Instead, we're left wanting, our minds full of curiosity and wonder.