Well, if you want more answers to your question, you might want to click on the "forum list" and post on the childfree forums...not too many folks get back here.
However, on your question, I am 37. I always just assumed I'd end up married with kids, until I really thought about it...right around your age actually. I realized that yes I do enjoy children, but no not all the time. It's basically about the difference between "need" and "want". Some people do feel a driving need to be parents, some people simply want to have babies. Either way, if they go that route, they end up with children that they will have to deal with, whether they actually like having them or regret having them.
There were times when I would feel slightly maternal and think "Yes, I want that" when I was around well-behaved children or functional families. However, the crux of my ability to overcome any maternal feelings that might rear their ugly heads on rare occasions is that I take humanity seriously. I think parents have a great responsibility to society as a whole to take their chosen path as parents very seriously, and actually do the best job they can to raise their children to be decent human beings. That means they do have to change their lives, it means they do have to modify their behavior, it means they do have to risk their children's ire once in a while and establish boundaries, encourage communication and critical thinking skills and say "no" to unreasonable demands.
Also, breeders have ruined children for me. I don't like our society. I don't like that breeders expect "the village" to raise their child. I don't like that breeders want to be a "best friend" rather than a parent. I don't like that breeders don't seem to make any effort to teach their children anything. I don't like that people have children simply because they "want" a baby, or they are curious to see what they can make with their partner, or they need to "carry on the family name", or they need a kid of a certain gender, or "someone to take care of me when I'm old", "I'm magically pregnant and don't believe in abortion or adoption" or any of the annoying bingos I've gotten in my life. To be honest, I've never heard anyone say say "I'm having a baby because I need to raise a child to be a productive member of society", and to me any other reason seems anti-society, anti-adult, superficial and false.
I think this is the case for a lot of child free people, no matter how they feel about children personally, they know deep in their hearts that raising a child is a huge responsibility that should not be entered into lightly. If you don't want to do all that work, it makes sense to us then that we shouldn't do it.