It comes down to teaching not bringing in money—enrolments (either domestic via the government, or paying international students) and grants bring in money (those requirements are basically "can bring in grants/other funding"). Even with ongoing positions, things like COVID (or even a change of focus) can cause the positions to end (and the ability to bring in grants would play a key roll in who stays and who goes). Any substantial change in the model is a matter for government, not the unis.