Australia had a referendum to become a republic over 20 years ago. While the majority wanted to become a republic, our Prime Minister at the time (a deep monarchist) asked the referendum question in a way that divided opinion about how a new president would be chosen, so the referendum failed. It was bare politics, that's the only reason. it then only felt that asking the question again (properly) would be somehow personally offensive to dear old Lizzie, so I think most Australians understood that once the queen died, we would move pretty quick to become a republic. I hope it happens soon. Although I think it will be inevitable - I Charles will gradually become less and less popular, and within 5 years he will hand over to William in an attempt to rescue public support but it will be too late.