Why do Australians always say 'mate'?

Again, Quora moderation has shown their gross lack of understanding of grammar and merged this question with that below. As a rule, Australians never say mate to a stranger (unless sarcastic), but they might to a friend.

Why do Australians call their friends “mates”?

I’m Australian and I don’t call my friends mates. I call my friends by their names. They may be mates or they may not be mates. A friend is not necessarily a mate but a mate should always be a friend. Also with gender, you don’t call a mate a mate, unless you want to lose that person as a mate. Also mate is mainly used by men for other men.

You might want to substitute another word like “buddy” in the U.S.A. for mate in Australia to see where the term mate fits in Australia. It’s just another example of Australia losing it’s character under an onslaught of external influences.