I think having kids reminds me a bit of playing high school football.
It looks really cool/fun (pre-kids). Then you realize how much time/effort/emotion/work it takes to be successful (kids esp small kids and you're not sleeping much). If you put in the time and effort in, it often pays off at the end of the day/on the field (teens/early adult kids).
There are no guarantees and nothing is certain, but I'd say most folks are thankful for making the choice to have kid(s). We have a larger than average family and we get comments from older folks wishing they had more kids like us. That being said, that is much easier to say later in life than when you have little kids and are feeling overwhelmed.
Maybe not the best analogy, but it seemed like it is in the ballpark.