Besides, having children is rarely a very rational decision. You do it because "everyone does it". There's a strong biological and cultural pressure to have children. And if you have one child, there's a strong pressure to have a second one.
Anyway, I find it's really important to find a way to have "couple time", as well as "me time". Grandparents, if they're close and available, are a solution. My wife and I regularly take child-free trips and weekends. I also regularly take days off to have "me time" and work on my personal projects.
I know this might sound judgemental, and maybe this is because I'm an introvert, but I don't understand people who do everything with their wife and children.
Even than, the joy you get with your own kid can not be compared with anything you ever had before. The job is very tiring yet very fulfilling. Don't think it can be explained until you experience yourself.
Now we have books like "The Baby Decision" that really helps people think about this and envision what it looks like on both sides of the fence. Even the decision to have more than one kid wasn't really thought about. Because you have one, of course you're having at least another one.
None of this was the norm. Go ask some people older than 50 or 60 why they chose to have kids. I would bet a lot of them didn't really consider another option.
For example, moving to a city, and then being envious of those who have lots of space? Or moving to the country, and then being envious of those who have all of the stores on their doorstep?