I don't know about Australia but there was an enormous amount of black market sports gambling in the USA before it was widely legalized. People who were unaware of this were just oblivious or led very sheltered lives. Broad legalization may have been a net negative for society but it's a complex issue.

define enormous? before it was legalized I knew one mate that was a gambler. I don’t have a friend anymore who does not sports gamble, hardly have relatives that don’t sports gamble. die-hard fans of teams now don’t give a hoot if the team wins (especially in the regular season)… not saying this is not a complicated issue but to say market was enormous is very much removed from reality