Exactly and if you are a state worker, you can only collect from the retirement system not Social Security. My SIL was a teacher and when she retired, she griped because she could not collect on her teacher retirement and her deceased hubbys SS. No medicare either.
Some places still aren't in. They make a bundle of bucks out of their alternative investments.
Oh, yeah, and federal government employees were not eligible for Social Security until recently (1987) and only if they were covered under the FERS system or worked sufficient quarters OUTSIDE the federal government.