College offers many potential benefits to students. The second post here does a good job of providing an overview of those benefits. I'd add that many people are interested in getting a self-directed course of study after high school.
College offers an opportunity to focus on specific areas of interest.
A basic premise about people is that they are all different. So, when answering this question, there will be many different answers. Let me give you a number of common reasons why students want to go off to college.
First, students want to go off to college, because they want an education and get ahead in life. Many people have been inculcated to believe that college will give them more opportunities. So, they go to college for their futures.
Second, some students go off to college for the sheer desire to learn. This is different from the first reason, because education may not be a means to a goal, but a goal in itself. Many of these people become teacher or scholars.
Third, some people go off to college for social reasons. They want to get away from home and experience independence. This is not a bad reason, because living alone can be a very important step toward adult life.
Fourth, some people go away simply to get away and be a twenty year old and experience life. This, too, is not necessarily bad. College, in my opinion, is a special time of life as you spend four years with peers.
Finally, I am sure that there are other answers, but the above four are some of the most common.
It seems that the coming-of-age in America is coming later and later in the last century. 100 years ago, many young people went out and made it on their own in their teens, not having (or needing) a chance to attend college.
Laws changed, unemployment meant more men needed jobs, etc., so that young people weren't as in demand as workers. So they stayed in school longer.
Now the concensus seems to be that you need a college education to get a good job. Unfortunately now, in this economic climate, many college graduates find themselves with no job offers. But it doesn't seem there has been time for that fact to filter down and help young people realize they may need to be much more creative than those who graduated even ten years before them in educating themselves. Perhaps more young people need to pursue starting a business for themselves. Or be very creative in following their own bents and gifts and finding a niche that will provide gainful employment for them. Or maybe spend time simply learning from those in their field of interest. A sort of apprenticeship, if you will.
There are many reasons young people like to go to college, but I believe the main one is that they simply don't know what to do after high school, not knowing how to get a good job with only a high school education. Perhaps we need to change some high classes so young people will be more prepared to enter the work force in creative ways.