Sydney (and to a lesser extent the other capitals) is massive: I think last time I looked it's the third the size of the Netherlands. There are a number of councils/LGAs in Sydney, one of which is the City of Sydney (https://en.wikipedia.org/wiki/City_of_Sydney). There is/was an attempt to reduce that number, for various reasons. A similar attempt was done in Queensland, which did make the City of Brisbane LGA (https://en.wikipedia.org/wiki/City_of_Brisbane) basically the same as "Brisbane".