Many of them do fail. But they don't go away. It's not uncommon for people to take it three or four times until by luck or sheer force of will they finally pass

Many of them do fail. But they don't go away. It's not uncommon for people to take it three or four times until by luck or sheer force of will they finally pass with barely satisfactory grade. Of course, this might be confirmation bias on my part. I never again see the ones that drop out.