Regarding the "extended hanging out at college", student loans contribute a lot to that as well. When I attended UCSB, the average undergrad stay was 6 years. While it was a good school, it was also right on the beach, so it was also a party central school. I saw two different segments that seemed to extend their stays past 4 years: First, the kids who had good loans, because it "wasn't their money" so why not hang around longer since they're basically getting paid to do so, since they didn't have to start paying the loan back till they were done with college. Second, there was a decent sized contingent of kids at that school rolling into the parking lot in BMWs and Mercedes and other expensive vehicles. Trust fund babies whose parents paid for school, the car, and often bought a condo in town for the kids to stay in. Again, it wasn't their money, so why not drag it out?
Both cases were kids who didn't have to take any fiscal responsibility at the time of their college stay. No fiscal responsibility, so no responsibility period. People who had to pay their own way as they went, or saw their middle class parents struggle to pay, were more likely to get out in 4 years because they had a direct connection to what it took to get them through college.