You don't get to choose whether you want to pay into Social Security and Medicare. If you work and file taxes you're paying into the system. Once you do, they're obligated to fulfill their end of the deal. Its up to the government to find the money. They can do it. Look at all the fraud they've been finding in government programs no matter where you look. Billions of dollars in fraud.

Social Security also pays for people with disabilities. I don't know if that is also included in the 1/3 figure, but that would be costly. With retirees, they only live so long. Some people don't even make it to 66, so the government wouldn't have to pay them anything.