Exactly. The lack of full time income for two years is a sizeable expense. Instead of being $40k in the hole after two years, they could have had $40k in the bank. At an average 5% rate of return, that is almost $300,000 after 40 years. That is loss of about $7,500 per year until retirement simply by spending time in school instead of at work for two years. You don't even need to get into tuition and other costs.

It was once promised that getting a degree would increase your job income by more than that $7,500 (or whatever number fits the situation). But incomes have been stagnant for 40+ years, with no sign of that changing. Without rising incomes, incomes simply aren't rising to compensate for the growing postsecondary educated populace.