Because QF is an end of the line carrier with a relatively small home market and a sparsely populated catchment area tie ups makes sense. No one flies via Australia to get some where else, it doesn't make sense.
A daily flight from each capital city to Singapore for the Asian connections, and a daily run to Dubai for the European/American connections would just about cover it. Time to start talking to SQ as well ?
Only London, Los Angeles, Hong Kong, Bangkok and a few other would be worth doing all the way with QF aircraft.
Emirates hub and spoke network can make money moving people between Perth and Paris, QFs point to point system can't.