This would explain the subsidy difference, I suppose...

If you thought farming arose because it offered more food than hunting and gathering, maybe you should think again.

People turned to farming to grow fiber for clothing, and not to provide food, says one researcher who challenges conventional ideas about the origins of agriculture.

Ian Gilligan, a postgraduate researcher from the Australian National University, says his theory also explains why Aboriginal Australians were not generally farmers.

Gilligan says they did not need fiber for clothing, so had no reason to grow crops like cotton. [More]

I dunno - as I study early farming the first indicators are related to domesticated food crops like emmer wheat, not cotton. Still his argument seems passable at least in Australia.

Overall, I would suggest this is going to be a tough dissertation to defend.