Cross-the-cultures

In learning more of other cultures by spending time with people from other cultures I've come to learn that we're more similar as in "The Human Experience", but we react differently to what comes along, our manorisms vary, specially in a new experience. But why must we assign certain traits or manorisms to an entire people or culture? We experience things individually. So one may carry their heritage and cultural norms with them where ever they go, yet their personal values/quircks/habbits mix in with any experience. Valuing uniqueness while trying to ignore stereotypes. Fun times either way.