I think a lot of these things are rooted in the fact that with technology, it's easy to kill boredom, either from TV, the Internet or Video Games.
Without these things, social interaction was the primary way of killing boredom, being single was very boring, especially once all of your friends got married.
Now there are so many ways to kill boredom, that there no longer is that motivation to go out and date and try to find a suitable mate.