Or maybe it's because the people who would be in charge of commissioning such large scale national projects, the Federal Government, are dyed in the wool denialists who cling to fossil fuels and will avoid being seen to support renewables at any cost?
And which party introduced and is committed to Snowy Hydro 2 and which parties condemned it?
Which party built Splityard Creek pumped hydro storage back in 1984?
Which party cancelled the building of Wolffdene Dam causing massive water shortages in SE Qld and has refused Federal money for new dams in Qld for the last four years?
"mega pumped hydro storage" is valuable but restricted as to sites - many of the best ones are along way from the users so you incur transmission losses - and it's not much use in say the Netherlands or Denmark.
The ANU have identified 22,000 sites in Oz as potential pump hydro sites. I don't think transmission losses would pay much sway in the building of these storage sites.
ANU Research