Why should you not have kids? Let me count the ways... Well, Dirty Writer came up with 10, stuff like "They Are an Economic Drain" and "Once they are Born you are Pretty much Stuck with them". Mmm hmm. Go ahead and read them; just wake me up when you are done.
Back? Okay, those of us with kids can probably give you a whole lotta better reasons to put the lock and chain on the uterus or the sperm tool, depending on your situation. Rachael rattled off: "bad for sex life, stinky, bossy, fluffy, they take away everyone's attention from YOU" in about 30 seconds. She also had one of my top reasons in there, "bad for the hoo hoo" which I'll underline by saying, think to yourself: do I like my vagina? Because it will never, ever forgive you. Unless you go c-section, and that's its own can of worms.
I'd add to the list: deflated boobies, having to talk to strangers who admire your baby, lugging a giant diaper bag around for years, your poor vagina, mom jeans, kids can cramp your dating style, you won't be able to watch or stay awake in a movie for decades, stories of serial killers and nature shows will devastate you in a new way, your poor vagina, they like to make you look the fool in public, you never get to hoard your sick leave or vacation again, your poor vagina, you'll plumb the depths of your own sleep-deprivation-induced rage, say bye bye to a restaurant meal that doesn't involve crayons, MILPHs, and of course, your poor, poor vagina.
Any we missed? I bet we could add another bajillion or so.