I can agree that having a degree doesn't prove that you're more intelligent than anyone else. I do believe that earning a college degree shows a desire to complete a task that is set before you. Dan, you mentioned that much of what's learned in college isn't practical for your everyday life (and academically that's true). As far as math goes, most individuals would do better with a true mastery of basic arithmetic (addition, subtraction, multiplication, and division) than they would to learn calculus. The beauty of someone learning calculus however is that, while most people realize it doesn't make them more well rounded, and you're not going to pick up chicks with it, you can still show that you've completed something that is both challenging and not particularly enjoyable.
As far as diverse people, college helped me be introduced to individuals from all across the country and the world. Not everyone that i met during my college years was an upper middle class, twenty-one year old, alcoholic. (however i knew plenty of them as well). But many of my classes were filled with mothers, fathers, working adults, athletes, scholastic scholars, etc. People who came from the "rough" side of town, and people who came from the Beverly Hills. I can honestly say that i've seen more diversity in college than i've seen in my typical jobs.
I do agree that life experience is worth something, in fact, it's worth it's weight in gold. The problem is, that when you apply for a job, you're probably sending in a resume. If your resume states only the previous occupations you've held, but mentioned nothing of "certified mechanical technician- Yamaha, Honda, Kawasaki" how do i know that you worked for a reputable company, or, if you just dabbled with fixing outboard motors on your weekend? Also, i can't expect an employer to go through a process of "weeding out" applicants based on any quantitative number of life experiences.