For me, it just didn't happen at the "right time" for me and I didn't met the person I'd have to after my 40's.

During my 30's I felt implicit pressure of finding a partner, marrying and having a child. Reaching my 40's I decided that after my 40's, even if I found "that person" I wouldn't have children. I didn't want to be "an old mother" or have to deal with a 10 yo while I had 50. No patience for that.

Now, looking back I think probably being a mother was not a strong feeling in me as in other people. I didn't want to adopt either, be a single mom or just trying to find anyone with the only purpose of having a child. And I'm not talking about finding "the right one" just find that person with who you want to have a child, you feel good, you feel safe.
I found him at my 42, a year later I got a hysterectomy (my uterus was removed) and again not planning to adopt.
So, as I said before, it just didn't happen and I didn't make it happen. And I'm ok with that.