Given that a large part of most degrees is pretty irrelevant to the student's future career 3 years seems plenty. If you're going to be an academic you can just do a masters or get on with your PHD.
{The downvote is a great example of this fascination. Merely asking a question was troublesome enough for someone that instead of responding to the question they clicked the down arrow. My question was polite and genuine, at least that was my intention. What is so threatening/offensive about my question?}
Another of my friends was an English major; planned to go into teaching but found himself in med school a few years later.
It's always a pretty wide variety, but I feel a large number of people end up heading another direction at some point, if not right after college.
(I too was a PSC major and ended up doing my 1L year before wandering elsewhere)
Personal story: I went to high school in France. When it came for me to decide between colleges, I had the choice between a 3 year degree at Cambridge and a 4 year degree at Stanford. The Cambridge program was for "Natural Sciences", Stanford didn't ask me to select a major until 3 years in. I chose Stanford, took a wide variety of classes far outside anything i had been exposed to previously, and ended up with a degree in Economics -- in addition to a BS and an MS in Biology during which I had the opportunity to pursue many courses in CS, statistics, data analysis, etc. It was also fun, so much so that I ended up staying 5 years instead of 4. Today I work in tech. Had I chosen Cambridge my perspective (and my life!) would be very different.