A recent article in New York magazine on parenting, All Joy and No Fun spends a lot of time on the research about how parenting is not particularly fun. The transition of children of modern from an economic asset to an accessory "Economically worthless but emotionally priceless,” says one Princeton Sociologist. “They’re a huge source of joy, but they turn every other source of joy to shit,” says some psychologist.
“There’s all this buildup—as soon as I get this done, I’m going to have a baby, and it’s going to be a great reward!” says Ada Calhoun, the author of Instinctive Parenting and founding editor-in-chief of Babble, the online parenting site. “And then you’re like, ‘Wait, this is my reward? This nineteen-year grind?
Later they discuss how happiness (pleasure) and reward are not the same, and spend time separating the two. In these scenarios parenting and having kids comes out looking better. Women with kids are less depressed. People who don't have kids often regret it.
In the quadrant of things people found both pleasurable and rewarding, people chose volunteering first, prayer second, and time with children third (though time with children barely made it into the “pleasurable” category).
Self reporting is always suspicious to me, what people say versus what they do is often far more revealing about what people actually value. More importantly, this academic drive to reduce every emotion to "happiness" — really let's just call it "utility", as the reductio ad absurdum of all human drives by economists, those other social 'scientists', prefer — is silly. The 'self' has a complex set of overlapping drives and agendas. It changes over time and by situation. Attempting to reduce all those agencies into a single overarching value of happiness misrepresents what we are.
But, have no fear. If the desire to have children fades for some, only those for whom the desire remains strong will procreate and eventually all will be right with the world. And if it fades away for all, then our species will fade as well, and once again, all will be right with the world.