Young people have a light burden, and all they have to do is fight for the future. He chooses to receive higher education, and the cost he needs is only the time cost and the possible opportunity cost, and the opportunity cost is unknown.
For a year, he will benefit from higher education for a long time.
For a relatively old person, he may be responsible for supporting his parents, raising his wife and raising children, and generally speaking, older people have relatively stable jobs and incomes. So the cost he needs is not only time, but also a relatively clear amount. Moreover, the responsibility of life lies in stress, which is an important reason why he gave up receiving higher education.
On the other hand, for the elderly, after receiving higher education, the benefit period will be shorter than that of young people.
To sum up, the cost is too high and the income is too small, so the elderly are more reluctant to receive higher education than the young.
I haven't studied labor economics, and I haven't even touched the most basic macro and micro economics for a long time. It's just some personal ideas, hoping to help you.