Sure, but take a couple struggling to have children for example, do you expect them to work every hour God sends only to be taxed to pay for the children of other couples? Bit of a kick in the gut.
Do you also want people to pay for other people's pensions all the while knowing that they themselves are probably not going to be able to retire without taking out a private pension? Another kick in the gut.
And public sector pensions are index-linked and guaranteed. There is a reason they are 'gold-plated'. They are not costed so the money isn't set aside beforehand. They are also not subject to inflation, they're instead kept in line with inflation.
And yes, it is an Americanism. It's also a Frenchism, technically. Any country that has had a revolution and thus is comprised of created civilisation, ie synthetic as opposed to organic, that also has a codified constitution like the American Bill of Rights, has a social contract. America is only 248 years old. Canada is much younger than that still, but I digress. It's a very complex thing so I'm not entirely surprised people think we live in a social contract society. The illusion is definitely there, but the actual concept itself doesn't exist in this country.
Yes, I want National Insurance to be optional. I want to pay for my own healthcare and that of my family, not that of complete strangers. I'm sorry if that comes across as offensive, but that is how I feel and it's what I want.