The overwhelming majority of the high IQ are not Mensa members. They are academics, doctors, lawyers, successful businesspeople, the kinds of people for whom it is more common in their friends group to have a Master’s degree than to be a high school dropout.
Those people are called academics. The kinds of Master’s degrees that are rent seeking credentialism, MBAs, MSWs, M.Ed.s are far more common than consolation prizes for those who didn’t get their Ph.D.