Allrounders just aren't in vogue in Australia. Basically, if a player shows ability with bat and ball, they're picked and watched until it's discovered what they're better at. Then coaches insist they concentrate on that and forget about the other thing.
Ironically, Aussies also have the propensity to pick batsmen who aren't quite good enough to make the main side, tell them to start bowling and then start picking them as 'batting allrounders' to justify their inclusion in the side.
It's all in the attitude, really. Aussie selectors are supposedly crying out for an allrounder of Test class but then they do the above and ensure they'll never see one.