Why didn't Aboriginal Australians invent agriculture?
They did.
Indigenous Australians were farming eels over 6000 years ago.
These traps involved building channels, dam walls, pond areas for aquaculture and cover a significant ground area (stretching over a 30km length).
Hundreds of tonnes of basalt blocks were moved to create a 200m long fish trap channel:
First reports of these channels and ponds, by government explorers in 1841, were ignored or dismissed as evidence of irrigation by an earlier, more advanced people living in Australia prior to the appearance of the Aborigines. This may have contributed to the erroneous belief that Indigenous Australians didn't invent agriculture.
Recent interest may possibly lead to eel farming, fishing and selling on a commercial basis.