Because generally, older people have more experience than the young, which translates into knowledge about the things that really matter.
When your life is falling apart or you have to make a life-altering decision, you ask your parents or your grandparents, not some teenager. If have something that absolutely, positively must be done, you give it to a senior, not a green newbie.
Age often (but not always) translates into knowledge, and sometimes translates into wisdom.
Look at those running for president this year. Biden, Sanders, Warren, and Trump are all old. I'm pretty sure that almost everyone will say that at least one of those candidates does not display wisdom. (Which one may vary, but nobody thinks that they all are wise.)
When your life is falling apart or you have to make a life-altering decision, you ask your parents or your grandparents, not some teenager. If have something that absolutely, positively must be done, you give it to a senior, not a green newbie.
That's reality. Ignore it at your peril.