A friend of mine from high school once told me that he never understood why the seniors never came back home to visit, until he went away himself. I like roast pork a whole lot. Regardless, and I know this from my own experience, the call of a family can be very strong. Now think about it from the perspective of the folks left behind for whatever reason. And, of course, the universities and colleges are a convenient scapegoat.
More people just get in the way.
Next, you get the other folks working - plumbers, electricians. These other crews are similarly arranged, though I couldn't tell you the proper number of people in any one set. Regardless, all these folks are members of skilled trades, and college degrees are uncommon among them. Just think about it. Since we're still a free nation, reasonably well, I think.