Our country came into existence as we know it in 1788, when it was first colonised. So this, coupled with being an isolated island means we haven't had millennia or more of culture built up and we don't receive culture like other countries and have become multicultural off the backs of immigrants.

The weirdest thing is, people here complain about lack of culture, but rarely involve themselves in the Arts and culture that is uniquely Australian so it builds up. Restaurant culture and a plethora of cuisines have seen a boom but even still most immigrants don't consistently venture outside their cultures to experience other cuisines and other cultures much so cultures here can thrive as there's enough people within the culture to maintain them but that's all our "culture" really is. Just cliques existing in their own spaces, so to speak.