Grey Power and NZFirst are trying to put the idea of subsidised health insurance back on the agenda - refer this article in the NZHerald, by Nicholas Jones (if you have a subscription).
The rationale advanced is that a person buying their own health cover is reducing the burden on the state health system. That is true when a hip operation is done at Mercy Ascot instead of Auckland Hospital, but it doesn't apply to all services. Many primary services are just not offered by the private sector. The other is that the insurance and rebate approach really comes unstuck for the highest cost groups - including the elderly. Their care is massively subsidised by the rest of us, it has to be: something like 50% of all health costs can be consumed by a person in their last years of life. Modest rebates for older lives are really unlikely to make much difference either way to this equation.