For what it's worth, my first trip abroad was to Mexico, while I was in college. No passport required at the time. My next trip abroad was to England while I was in graduate school. I was originally planning to go to California (from New Jersey), but found it cheaper to fly to London, and I had some friends there I wanted to see. This was my first ever requirement to have a passport.

(Annoyance: at the time I got my original passport, I had long hair and a goatee. I nuked all that a few years later, but passport photos last ten years. This made some airport immigration officers look at me funny, particularly in Canada. There's something about Canadian immigration. No other country seems to care that much about who shows up.)