Well fancy that 9th December 1967 ! ! !

The general reason is that it was popular with English crowds and became an expectation, or a marketing tool if you like. Then as the decades rolled on it became a tradition that most people had forgotten the roots of. 1967 is a key year for indiginous Australians as they became citizens by law, and as freedoms came back to them through the 1970s I guess the Australian warcry was viewed as culturally insenstive.

The roots of it are thought to be that New Zealanders who played for certain rugby sides, notably Newtown, in the early 1900s helped to create war dances for their clubs, and one of these was adopted by the Wallabies as a response to the New Zealand haka. It wasn't particularly popular with the players. However, when the All Blacks toured Britain in 1905, which was a very successful tour and huge for the growth of international rugby, their Ka Mate haka was a notable curiosity and seen as part of the draw. So, the subsequent Wallabies tour, and the Professional All-Blacks and Kangaroos tourists, also adopted this pre-match ritual. As time went on, tastes changed and it came over as ridiculous but traditions are hard to break.