The human desire for sex and for inter-personal relationships is dulled by the ability to have porn stars in your own bedroom, and the ability to put the headphones on and play games and chat with your buddies online. This kind of feeds into or reinforces the instant gratification theme. I just think there is less of a desire to go out. When I was young, I was always in search of a party, or a place to go...and so was everyone else, so we were all searching for connections through direct personal interactions. I don't see that with the upcoming generation...at least, I see it much less. A buddy of mine said his daughter is wondering where the men are...she can't meet anyone. (And just so you know, I've met his daughter, and the problem is definitely not her.) While this may not be uniformly true, I do think it is statistically significant. Porn & electronics were ubiquitous in Japan first, and their population started crashing first. Korea, the US and the West have followed the Japanese model.
I'm setting aside China because their population crash is because of heinous government policies, and doesn't apply to the West. China is 1984, where oppression leads to the problem. The US and Western Nations are Brave New World, where the pursuit of instant & easy pleasure leads to the problem.