In my opinion I do not think it is logical to lump all "so called" crimes in the one basket.
So someone who has been caught soliciting a prostitute in Australia is put in the same category as a murderer, a armed robber, a drug dealer, an arsonist, a rapist etc. Just as well the Australian justice system sees fit to fine the person soliciting a prostitute and not record a conviction against their name.
And why would the USA care about someone who has not had a conviction recorded against their name?
In some Middle Eastern countries it is a criminal offence if you have committed adultery. So now you have a criminal record and would be not be allowed entry to the USA. Yes sounds very logical to me.