Jeepers, its from the days when horse carts were used to deliver stuff, like Beer, and all those other things that make life possible.
Trams in the centre of the road continued the use of this method of turning in the centre of the Melb. CBD.
They were Cable Trams, before they were Electric driven. Sydney had Trams too, not sure if they had any similar movement/turning rules.
Bird may be able to help with info..
Not sure if he'd want to or if he's still rolling on the floor laughing.