Also I don't see how the neoliberals can't see that within a few years of implementation, productivity would jump massively as more people would be able to participate in the economy and therefore generate so much more value.

I should stress, that shouldn't be the reason for implementation, you know the usual ones about why decent healthcare should be available for free/at subsidiesed cost (depending on which style of universal healthcare implemented): it's the morally right thing to do under the hypocratic oath, every other developed country does this, etc.

But it's a cold economic reason that makes sense.