Even if you don't have a degree in your field, college offers an opportunity to enhance your own critical thinking and problem solving abilities, which are paramount to success in some fields.

Also, one has to consider the shifts in education that seem to be focused more on graduation rates than quality graduates. In such a situation, graduate school becomes the new undergrad, and undergrad becomes the new high school degree. This isn't everywhere, but that seems to be the general trend across many markets: a four year degree is become a minimum qualification.