The whole point of GLS is to provide a cheap and certified accurate precision approach to an airport without the need for local antenna installations for localizer and glideslope. And once you have it for one runway, you can have it for all runways, even including other runways at other airports within a certain radius.
If noone has the equipment to use the technology then it is useless regardless of how good it is. The problem in Australia is that the places where it is most useful, country areas, none of the aircraft flying in there are ever going to be capable. Unless the government wants to pay to retro-fit every SAAB, Dash-8, Brasilia, F-100, F-50 and all GA charter aircraft with a GLS receiver and pay for the charts what's the point of it?
Just because something is a great technological achievement doesn't mean that it is necessary. You would be much safer, and have a more pleasant driving experience in a $180 000 motor car but I bet you don't have one. I'll bet you probably don't even own one half that value.