Christians raise their kids as Christians because they were raised as Christians. It's like the testosterone-pumped dad that wants his son to be a big football star. Same thing.

I think Christianity is a well-timed joke that has lasted way too long. However, I do think Christian principles exist in the world. The world needs God to scare the believers away from anarchy. Perhaps Christians bring their kids up as Christians (besides my first guess) because they honestly feel that Christianity is good, and that they want their kids to be good. They really think that their beliefs and values are solely the product of Christianity, and not the product of everyday etiquette or common sense or sensibility. They really think that Jesus is a path that should be not only theirs, but their kids' as well.

If you ask me personally why I think Christians raise their kids as Christians (like in a dark corner in a restaurant or something), I'd whisper "It's because they're selfish, shallow, narrow-minded, restricting, unenlightened, deluded, diluted, misinformed, and ignorant. In other words, they don't know any better." Just plain honesty. I wouldn't say it unless I meant it (or I thought you'd think it was funny).

Fear is your only god.