That's because tram (and train) drivers are not trusted to run a service
with out 'supervision'.
Tram drivers can not 'run on sight'. Trains can't proceed if they don't
have comms to the control centre
(ie the entire Sydney Trains network coming to halt because the train
radio system went down due to a bad software update - signals and
interlockings were all fine, but 'no communications, no movement' )
I assume Randwick control had another fire alarm and again hand over to
the Moore Park bunker failed.