If you mean the Australians, at this point it is force of habit coupled with a bone deep -- and justified -- fear of the consequences for defying the law. Anyone bucking the system is risking everything. To rearm themselves would require a massive undertaking and it would have to start in small towns and isolated regions via weapons smuggled into the country.
This may very well be happening; but it is far easier to remain armed than it is to become armed again after giving up your weapons.