I assume you don't get out of Australia much? In my experience, the concept of a national ID card is more popular in developing countries where computerised databases of their population did not exist prior, and even in most of these countries that have elected to have an ID card, the actual ID has been optional if other forms of identification (licence, passport, etc) is held, and they are not required to carry it with them at all times. I appreciate that a national id has its virtues, but the cost to implement in a country that wouldn't see any immediate benefit is just ridiculous.
Your second point re: requirement to show ID is also more wishful thinking on your part rather than the "law". Police are entitled to ask any person for proof of identity if they have reasonable grounds to do so. No one is obliged to simple provide their passport on demand.
