It's not all discounted future cashflow, it's discounted future utility. And a lot of people get the best part of their utility from family, friends, and relationships. Finding a reasonably prosperous position from which to secure a future with your family may be the best investment one can make.

Academia's contribution to that position is a murky proposition (added debt without added earnings potential undermines financial security). And while there are certainly immediate rewards from the pursuit of intellectual goals and from your friends at university, you can also get not-too-dissimilar rewards and more cash doing something like programming computers. And then you can use the cash to do things like: honeymoon with your wife in South America, enroll your child in a really good arts or music program, or spoil your grandchildren with a study-abroad semester in Europe.