Bigdirt,
Like Nanon, my decision not to have children is a complicated one.
I think my first real influence (against) it was watching my own mother and father try to raise two children. They were 16 1/2 and 19 when I was born. My mother got kicked out of school because she was pregnant...even though she was a straight A student, in the national honor society, and taking college level courses. They still did that in 1969....and she never got a chance to return to school (she's taken a couple accounting classes, for work, at a CC but nothing more). My father was "forced" to join the military during the vietnam war just to support us. Then came my pre-teen years, when I discovered that I'd MUCH rather play football with the "guys" than sit around babysitting other people's kids, unlike the rest of my girlfriends (I thought of kids as "screaming demons")!. Once I hit high school I watch NO LESS than 6 of my girlfriends/classmates get pregnant...and subsequently DUMPED by their (longtime) boyfriends. One of those boyfriends happened to be my BEST friend and I was SO disappointed in his actions that I didn't talk to him for 2 years (they were 19 & 20, respectively, engaged, and when they first made the "announcement" he acted like the happiest "daddy" in the world....he cheated with a "dancer" when she was 8 months along).
Now couple all of the above "negative" influences with the fact that I want to travel, don't want to go through labor pains, and don't feel like looking like a whale for nine months (and possibly forever, given my genetic makeup!) and it's easy to see how I came to my conclusion. Luckily, the man I choose to marry doesn't want children either, so it's been a pretty easy decision to live with.
Besides, I DO have a maternal instinct (a STRONG one)...it just happens to be directed at things that have fur, feathers, or scales! I've also changed my "attitude" about kids now that I'm older and almost all of my friends have them. I love to be around kids...for short periods of time. When they get cranky...I send 'em home!