That is certainly true, Telesphorus. Navigating social circles (some, not all) is like walking through a minefield of deception, so it isn't hard to see how people can quickly become disillusioned and unable to trust others easily.
The issue is very complex, and has a lot of layers to it. Feminism, immaturity, and dishonesty all play their part, as well as a general scorn towards family life.
Marcelino: I would pray for your single friends, and hope that they are living holy lives, which is certainly possible if they are single for unselfish reasons.
Spiritus: Very true. I was speaking more as a generalization, much of society has an issue with staying single for bad reasons. One look at the rising birth rate among single women is a good indication of the terrible trend.
As for marrying at 18...I wouldn't rule it out. If the couple is mature and has a good understanding of their duties toward each other as husband and wife, then I don't see the issue. If, however, they are immature and just want to marry for the experience of it, or due to base passions, then there would definitely be room for doubt, which would be true at any age.
It was not uncommon for people to marry at a young age, even in fairly recent history. If human civilization has marched forward without collapsing thus far, I think it's probably safe to say that marrying young is not a major issue.