Jetstar Asia doesn't allow passengers with disabilities either, at least that is the official stance. Works in Singapore/SE Asia. We all know that if they do that in Australia there is a good chance of a discrimination suite.
LCC's are not set up to cope and the cabin crew are not trained to deal with it.
You want a wheel chair to meet the aircraft on arrival in Singapore? Be ready to pay S$40 for the service. Oh and by the way, be prepared to wait.