On a Roth, you paid the taxes up front, when you deposited the money into the account. 

Retirees live off a lot more than IRAs. There are taxable 401k's, 401a's, 457b's, plans, and plain old regular savings accounts. Up to 85% of Social Security is taxable depending on your income level. My mother paid lots of taxes on her $49,000 of annual income.