you have kids for completely selfish reasons -- you're egotistical enough to think that your genetic material is worth passing on and to live vicariously through them when your youth is lost. you want them to succeed where you failed. or you're trying to intellectually justify a primitive need. either way, it's all utterly selfish.
my wife and i had a daughter because we were curious and naive -- could we actually raise a kid? that got answered pretty quick -- yes, we can -- and now we have a good 16 years (probably more, if some of you are anything to go by) of utterly decimated free time, additional financial obligations, and a whole new source of pure razor-in-the-guts stress. i love my daughter dearly -- she is super smart and super cute and i see a lot potential in her -- but did we have her out of some sort of enlightened rationale? no, we had her out of ignorance. we're living with the consequences of that ignorance, and refactoring our lives to make sure our selfishness doesn't impede her, but until you've had a child, you'll never know the high cost of that refactoring.