I have a long thing I could post here, but instead I will just say that recently, I realized that my kids have taught me the value of not knowing things. It's not essential to anyone's existence, or even happiness, but it's a thing that would never have occurred to me if it weren't for my babies.
I believe that one should not have kids unless one feels a deep and inexplicable need to do so -- I know too many people who are parents by accident or because "it seemed like the next step" -- but I would argue (and I know you parents on the board will agree, in your more serious moments) that they do add a lot to your life beyond the cuteness factor when they're young. It's not really about being happy, so much as it is about getting the chance to look at life in a different way.
I guess that's why so many people who don't have kids travel extensively, or have really interesting hobbies, or do a lot of volunteer/charity work. They're all (equally valid) different paths to the same goal: being part of something bigger than yourself.
Too bad a lot of people with kids think that people who chose not to have any are self-centered child-haters. Dunno if you non-parents know this, (though how could you not?) but a lot of breeders view the child-free with equal doses of pity and scorn.
Sorry, we can go back to talking about how kids are aggravating balls of noise, laziness, and disease.