That's not really a coherent statement.

If people don't even know it, it's not part of the culture.

Who are the “people” that you are referring to?

This makes total sense to me. There is no monolithic “culture”— there are multiple related cultures, differing little in essence but differing greatly in the details. And each individual is usually only partially ignorant anyway.

Culture changes, too, and asymmetrically. So the “done thing” may be done be very few anymore.