Rarely - toddlers are the highlight of the game for me. However, sometimes I'll want to try a particular gameplay aspect that doesn't work well with kids, so instead of having my YA have kids immediately, I'll turn off aging while she does something else.
One thing that's hard with kids in the game is any situation in which your Sim has to travel. Kids and teens have to be home in order to go to school, and while day care works fine in my game (the toddlers come back with hunger in the green, and even learn skills), the whole point (to me) is to nurture and teach the toddler.
No kids of my own, either, and never wanted them.
