That because most pubs in Oz are licensed as hotels, which mean they have at least 4 different bar rooms, with such things as a beer garden & a dinning area & a pool room, entertainment room, TAB betting agency, oh & a poker machine room to. Plus as such they must provide at least 4 rooms for rent under the hotel license, but half the time they rented them to themselves. Some pubs have tavern licenses, which mean those ones don't have to provide accomadation.
This all eveolved from the days when pubs were inns & there was always a pub within one days ride of another pub.
Even now though there are plenty of pubs in Oz where people actually have long term rental on a room (rooms in pubs are useally cheap).
I lived in a pub for about 6 months on & off about 15 years ago. Actually all 3 of my local pubs have rooms for rent. But you wouldn't know otherwise, with 2 of them as one you have to enter to the accomadation part via the drive-in bottle shop at the back & the other one you get to the accomadation part via stairs behind the counter in the public bar.