There are far too many people who really can't save for retirement due to low wages for a significant part of the population. We aren't going to let these people live in abject poverty, and they aren't going to have any money to cough up to support themselves.

It's the same for Medicare. Paul Ryan wants a premium support system where seniors receive part of the cost of their insurance premium from the government and pay the rest on their own. For many people, the will absolutely not have the money to spend on this. If they can't afford it, they will go to the emergency room and receive care (they legally can't turn you away) once their condition becomes severe enough. We can either force the hospitals to care for these people (and jack up the prices for the rest of us to compensate) or we can have a sane system where we all pay a reasonable price and split the burden over a larger population.

I'm not arguing for some European style social welfare system. I think we ought to have a system that comports with the laws and norms we have in place now (norms/laws I understand: people can go to the ER and get care regardless of their ability to pay, elderly folks do not live in poverty).