Well it would never be passed into law in the USA, but I can't see the harm in protecting Aussie workers entitlements, when the employers are trying to take that away from them. 4 weeks of vacation really isn't much. It's simply setting minimum standards (just like the minimum wage in the USA), of course employees are free to negotiate for better if they can.
What I've found in the USA is that workers almost feel guilty about taking vacation days. Aparrently most workers don't even use all their vacation. The obsession with long work hours in unhealthy IMHO. You are going to get more out of your workers if they are well rested, and in the proper mind-frame for productive work.
I can certainly see the argument that someone can do more in 7 productive hours than trawdling along for 9 hours, just watching the clock go round.