You do know that regional NSW and QLD is more than just Newcastle, Gosford and the Northern Rivers right? You would be including places in Western and Central NSW/QLD and I could assure you that the economic factors (earning potential, unemployment rate etc) would definitely be worse there than in Adelaide.
Also, according to this article houses are expensive in Adelaide as well
amp.abc.net.au
Other people in the world also don’t seem to think Adelaide is too bad to live in
www.australia.cmu.edu
Anyway, this is completely off topic now. I agree with you that Adelaide is definitely not the most pressing place in terms of expansion, however there are plenty of places in Australia that are worse than Adelaide.