"Why not only perform the "Welcome to Country" for international events?"
That makes no sense?....Don't locals attend test cricket? Or other test matches whether it be NRL or Union ?
The term "country" for Aboriginals is not the same as new arrivals like you and I. Aboriginals had about 500 different countries within whats now been called Australia by the Brittish. Their welcome to country reflects a welcome to their historical area which they are still connected to. Nothing more and nothing less. It really shouldn't be a source of such angst.