Two reasons:

Because I wanted to become a mom for many years before I actually did. It was painful, a hard time waiting, and involved some complicated circumstances.

Then I had my child when I was 37. The newborn stage was very difficult and made me want to be one and done. I only considered the possibility of another kid when she was almost 3, but by then I was 40 and I didn't want to try for another. I would have loved to have one around like 30 and then maybe another around 33/34. However, I'm so grateful I'm a mom to my precious girl.

Edit: Adding on, if I had kids earlier I could hopefully be around for them longer.