There is something seriously wrong with society if people in their youth and most child bearing ages are involving in casual sex rather than building a family with a partner.

When you are young and energetic, a lot of people tend to drink and party and sometimes hookup and have casual relationships.

Hookup culture and casual relationships as well as serial monogamy are strongly present in western mainstream culture.

But if we look at the reason that we have so much energy in our youth and are able to stay late into the night its because we are of child bearing (and rearing age). Looking after children takes up a LOT of energy. It takes up a lot of time. You may have to wake up at night for your crying child. This is why you really have all this energy. Instead, people waste that on partying and fun.

A lot of people have kids later in their 20s and 30s but then you start to have less energy and tire out wuicker than before.

I believe this might actually be one of the reason why so many western countries have below replacement level childbirths. Its not just economic reasons. Its that as you get older you just cannot do it anymore.

I think we are doing this whole thing incredibly wrong. Normally, we should be finding a partner instead of keeping things "casual". We should also be having kids a LOT earlier. And then by your 30s you should ideally be done having kids. Biologically speaking, at least.