[defrost]

The ones we pay our taxes for?

They're not exactly burdened by extreme sports injuries, most surfers, for example, are injured crossing roads, in car accidents, or at work falling off roofs, etc.

( source: one of https://en.wikipedia.org/wiki/Fiona_Stanley conversations back in the day )

[notheyarent]

Citizens have an obligation to act responsibly when they partake in broad social contracts such as shared health care and insurance. Such a society must regulate access to areas of extreme danger (disused mines) to stop mentally unwell citizens from endangering themselves but more importantly endangering their fellow contract holders.

[defrost]

Nah, we're right there thanks mate.

The whole inland gold belt region is filled with abandoned shafts and it's rare anyone falls down them.

What's the cost benefit in fencing off tens of thousands of individual pre existing shafts and to what degree of robust security construstion do you recommend? More to the point, what's the tax payer out of pocket cost for that?

You don't appear to have actually thought this through in any pragmatic sense.