I guess you mean penetrative sex. Unfortunately, solo sex is also a down of sex.

Nowadays, youngsters are more enlightened and they do have a sense of responsibility than the old reckless young people.

Before it was easier to get a woman pregnant and dumb her but now men are held accountable for their actions. So younger factor in child support and health insurance which are pocket draining when they think of sex.

Also, let's not forget people are busier and distracted now with school, jobs and social media to think of hookups, so they sex themselves to jack off.