I'm one of those people. In my late teens. just starting to come out, I began meeting other gay guys at a gay bar in Des Moines. (The drinking age was 18 at the time.) I made friends with a cohort of young guys in their late teens or early 20s, and a good bit of sex went on. Nobody had really heard of AIDS much, other than as some sort of mysterious "gay cancer" that seemed concentrated in big coastal cities. We didn't think twice about it, and the concept of condoms for gay sex was ... almost laughable. Condoms were for preventing pregnancy! For a good couple years, I had plenty of condom-free sex with people who might very well have been positive. Years later, when HIV testing became available and I had my first test, I was scared as hell. Since it takes a decade sometimes for symptoms to present, I knew I could very well be positive. When my test came back negative, I heaved a sigh of relief and then drew in a toxic lungful of survivor's guilt.

Nothing but random chance and an unpleasant early experience with bottoming (which was itself random) had saved me. I really never have figured out how to process that.