Listen, you're creating you're own argument. My original post was only to try to explain why so many Apple users like iMessages and find it difficult to leave--never once was I saying it was the best messaging solution, just that it's preferred messaging platform for iOS users in the US because of the reason I mentioned.
Second, I think you're confusing your own anecdotal experience using WhatsApp with fact. Unless the overwelming majority of Australians just converted to using WhatsApp over the last 6 months, the true number of active users is far less than 'everyone in Australia', according to this report. In reality, it appears to be barely higher that the percentage of US users.
Share of population in selected countries who are active WhatsApp users as of 4th quarter 2016
Regardless, let's not derail this thread any more with a discussion that's been had countless times in this and other forums. An awful lot of iOS users count iMessage as a signficant reason why they prefer to use iOS--no different that an Android user preferring to stay on Android because they like a particular aspect of that platform. It's OK not to understand why they do.