Let's start with a list of "Why Social Security is NOT like fire insurance":
1. It pays off the same amount whether you need it or not.
2. The "premia" are not risk based in any meaningful way.
3. If you don't "buy" it, you go to jail.
4. There is only one company that "sells" it.
5. The "insurer" can unilaterally change the terms of both the premia and the payouts with no recourse for the "insured".
Ok, so it's not really insurance. Then what is it?
Well it's two distinct components. The first is the payroll tax, the second is the retirement benefits. The payroll tax falls on the relatively young, and the benefits are paid to the relatively old.
The confounding problem is that many people believe the payroll taxes they pay go to fund the benefits they will receive, which is completely untrue. The payroll taxes go to pay current expenses of the US government. They are just a tax on labor. The government is spending every penny of those payroll taxes to pay for current expenditures. There is no meaningful economic sense in which the current payroll taxes can even be said to be exclusively funding the current retirement benefit payouts!
Going back to the (bad) insurance analogy, the insurer is free to use your premia to buy fighter jets and space shuttles!!
So, is Social Security welfare then? Well the payroll tax component certainly isn't. The retirement benefits part certainly is.
But I will say this; it's a type of welfare that I think we should have! Not in it's current form, but as a means-tested safety net, and without the strange fiction that it's financed by the payroll tax.
Keep a modified (for the poor only) safety net, drop the payroll tax.
Replace the revenue by cutting spending elsewhere (you're on your own President Karzai!!).
A 12.4% tax on labor is a dumb tax in an era where we are worried about employment and middle class incomes and sending social security checks to Warren Buffett and Bill Gates is, if anything, even dumber!