The men or women who actually know what they want when they were young, probably wanted someone much much older than they are. For example early twenties knowing and wanting someone in the late twenties or early thirties. Of course no one wants to baby sit a youngun trying to cultivate them for life. So it's a no go.
Then in current society those in their late twenties and early thirties, often are just as directionless as they were in their younger years. So it's a whole another mess.
People don't know what they want until they lost it, as it commonly goes. Those that know what they want, well are constantly searching for it. Cuz no one has what they want.
Even if a person just wants a nice simple life, the other person will want something complicated or find conflicts in life. If one person is very kind and helpful, they other person will simply take advantage of it. It's too rare to have an appreciative person who will in kind return such kindness in two folds.
So sometimes as it finally goes, let them be free!