Not wanting to stereotype too generally, but from talking to other Aussies about it we chalked it up to a higher level of self-confidence over there.
I know I definitely struggle to talk to strangers, though in part because you really just don’t know what you’re going to get sometimes! It was the part of travelling that I thoroughly enjoyed as a young 20-something. I was thrust into situations (hostels, bars, etc.) that forced me to overcome my shyness.