You raise a good question, but here’s the thing.

In Australia discrimination may be unlawful if it pertains to:

age
disability, or
race, including colour, national or ethnic origin or immigrant status
sex, pregnancy, marital or relationship status, family responsibilities or breastfeeding
sexual orientation, gender identity or intersex status.

religion, political opinion, national extraction, nationality, social origin, medical record, criminal record or trade union activity.

The kicker here is - insurance companies are allowed to – that’s how their business works.