Not sure about Australia but as dual Can/US citizens our family of 5 never once bothered getting Cdn passports as they are useless re-entering the US. Even while living in Canada we still just used US passport and nexus cards. Even the kids going to Cdn university used US passports. They carried around their little Cdn citizenship cards with baby pictures that never expire and they used these to get a SIN. Even frequent back and forth during strict covid lockdowns and banned Americans no one ever said anything. But Australia is probably different.