Bottom line is that it is ok not to get married and have kids. Many young people don't need this. It's a choice not a responsibility. That's the way things should be.
If the reason they are not getting married is becasue they are really the type of people that would be happier NOT having children or spouses, that is one thing.
If the reason they are not getting married is because of bad ideas and behaviors that have undemined the ability of people to form healthy relationships, then that is another thing.