Because they are the big cultural magnet in their part of the world with little fear of absorption, at the moment anyway. In contrast, we are the ones at the edge of a great whirlpool pulling us relentlessly in. The Ozzies are also more stroppy about authority and hierarchy in general, e.g. Ned Kelly, Waltzing Matilda, a bit like our American neighbours. The fact that we don't have intense sporting rivalries with the British attenuates the relationship as well - we are vaguely friendly.