People who've done cool things are much more fun to chat up. We need new adventures and new experiences. We need new stories and new things to talk about. We need to see new places and do new things. Stagnancy is the death of growth and once somebody's done college, there's really no point in hangin' around.
College is a cool ride, while it lasts.
Maybe we'll miss it when we're gone. But going out in the real world, even if it's horrible, is inherently cooler than just hanging around in college. There are, of course, empirical reasons to get out of college. Spiralling debt, skyrocketing tuition, low credit caps and good teachers getting canned, plus an administration and state government that doesn't give a fat rat's ass about it, doesn't sweeten the collegiate deal any. But when it comes down to it, leaving college is a personal choice.