Cultural Degeneration

Many lifestyles lead to non-reproductive dead-ends: excluding reproduction or replacing it with simulacrum activity.
Any anti-reproductive trait should lead to its own extinction - at least in theory. Why these anti-reproductive traits emerge and why they persist in the world?

>>17
Industrial civilization is not sustainable with majority being below 80-90 IQ.

because it leads people to do things like casual sex without reproduction

That only a specific aspect of specific culture where it happens. Its not inevitable path for any civilization and it only takes effect where leisure sex is without negative consequences(a fairly modern phenomenon).