Those pesky little ones??
ASA gets most of it's money from the major airlines, therefore they provide most services to the major airlines.
(airports are the same)
They have to take some notice of the little aircraft because they get in the way of the big ones. There the interest stops.
That's why they want us all to fit ADSB, so they can see us and tell the big fellas where we are.
ASIO, customs, police AUSAR and the military also have an interest in ADSB. (I'm not commenting on whether this is good or bad, just stating what I see as fact) The GA pilot and operator get a small benefit from it.
There is not even VHF radio coverage over the whole country.