Great OP, FlyingRamenMonster.
I would say it is very much a rite of passage in the US. The first American university, Harvard, was a training college for clergymen (as well as a place to “civilize” Native Americans). Well-placed young men went to Harvard from across the commonwealth to go through recitations and eventually graduate.
When they moved to campus, the university assumed responsibility for their upbringing. Students lived in houses near (or on) the campus. Tutors were responsible for overseeing and disciplining (usually quite harshly) students. There are great accounts of student uprising against brutal tutors who whipped or caned them. Essentially, this was the birth of in loco parentis - acting in the place of the parent, which is a philosophy that traditional residential colleges have assumed since 1636.
At the turn of the century (1900s, that is) there was heightened tension between students and administrators about the amount of control the institutions had over their lives (students could be expelled for trivial things like forgetting to turn in library books, while universities were held liable for damages caused by students at local taverns). By the 1960s in loco parentis had been seriously diminished, to the point that by the 1980s students could pretty much do what they wanted to do without reprisal from the university. Historically, in literature, film, and in the arts, going to college has become very much a rite of passage into adulthood for the middle class. (Military service might have a similar position for working class/lower-middle class families as well.)
There was a landmark court case in the 1980s that concerned a student who returned from a party drunk - and walked out of a third floor window, killing himself in the process. The university was found negligent, which re-introduced the issue of liability. So in loco parentis is a mixed bag here. Most four-year competitive colleges have some sort of residential program, but as many have described here, there’s a lot of variation. For instance, MIT was notorious for having a very relaxed residential system where students lived off campus in living groups or frat houses from their first year, but a series of high-profile suicides forced them to change their policy so that all first year students live on campus. It’s always been a requirement at Harvard for freshmen, and virtually all upperclassmen live in residential houses until they graduate. This makes sense given that the students at these schools are from all over the nation and the world, not just the Commonwealth of Massachusetts. Most couldn’t live at home because of distance even if they wanted to.
Most American college students pursue postsecondary education 100 miles or less from home. I think Dopers likely are skewed into the more selective segment of higher education, where they may have gone to college across the country to attend school, or crossed the state line. But that isn’t the norm.
My own experience - I am from Austin, and it so happens that there is a world-class university 15 minutes from my house. I actually chose to move out and live on campus for a more “authentic” college experience. Plus I didn’t want Mom & Dad monitoring my whereabouts now that I was a respectable 18 years of age. My high school class of 200 had about six of us at the University of Texas, and I was the only one who lived on campus. Only three of us graduated - I think being in the new environment, though difficult to adjust to at first, helped me be a better student. Plus my entire peer group was doing the same as I was - studying 24/7, rather than running errands for the family, fixing dinner, or hanging out with friends who made money but didn’t have to study for exams.
At UT Austin, the flagship institution of higher education in the state (sorry aggies), students came from all parts of the state (especially the big cities like Dallas, Houston, El Paso, and San Antonio). I was always one of 2 or 3 kids in a dorm of 1000 from Austin proper. Most students moved into apartments by their second or third year - another rite of passage.