All freshmen and sophomores are required to live on campus unless they get special permission from the school to live with their parents, relatives, or spouse. There are special exceptions (i.e. dietary concerns that require having a kitchen) for some students, but these are fairly rare; students are strongly encouraged to remain on campus until after their sophomore year. Junior and senior housing is available based on the amount of space. There are still some juniors and seniors who live on campus and do not mind dorm life at all. Some prefer to live close because of sports, jobs, or other commitments. It's all about preference.
Many may prefer to live off campus simply because you can have your own kitchen, your own living space, and an actual address, and are not always under the supervision of a RA or Head Resident. There are lots of nice apartment complexes within about 10-minutes drive from the University, and from talk amongst students who live there the landlords are "pretty cool." These landlords understand that their tenants are college students and are more lenient than the average landlord, so long as the students stay in legal boundaries. Usually there are never any problems with noise or parties at these apartments. When students are ready to move out of a dorm, and into their own place, Residence Life is there to help find good deals in local housing. Much of what you can find is located conveniently close to the University; there are even locations in Burlington and Gibsonville that are also close, but still get you out of the general Elon area. With all the options and affordable prices, plus the help of Residence Life, off-campus housing is not a difficult thing to plan. You just have to stay informed about when to look and lease.