This is, IMO, the best way of looking at it. Whether or not Uber's drivers are employees is a completely separate matter and your point stands regardless.

The consumer is paying Uber. Whether Uber uses employees, contractors, clockwork automatons or aliens to provide their service is irrelevant.

It's a little different in Australia. The GST registration threshold is $75,000, but there is a specific carve out for taxis that forces registration/collection of GST for taxis regardless of turnover. The ATO (and now the Federal Court) aren't challenging the contractor/employee position of Uber - rather just that the individual drivers should be collecting and remitting GST on their fares.

The same thing applies to Manpower or any temp agency.

"I call manpower, manpower sets the price, manpower charges me, and I pay manpower!"

Except in that case temp agencies are clearly employing contractors, and thus don't have to pay GST.

Not everything is black and white. If they were, the government would easily have been able to block their actions. Right now they're trying to figure out what's going on and charge them appropriately.

The Australian GST legislation specifies that taxi drivers MUST be registered for GST regardless of income.