SS is a product of law. It has been changed and amended by Congress and approved by the President. In 1983 President Reagan and Tip O'Neil changed the law by increasing the age for full benefits from 65 to 67. They also mandated that all new Federal employees would have to join the system. Changes are made all the time.
Yeah, in 1984 SS benefits were made taxable up to 50 percent. Then in 1994 made taxable up to 85 percent. We know where those changes are headed; to take more away and give less out. I'm currently receiving SS, but realize it won't always be there in the future.