> If one spouse stays home to watch them, that covers as many kids as you have.
That's debatable ;)
I have two kids, and taking care of both during the day is vastly harder - both mentally and physically - than working two jobs. As they say, it takes a village to raise a child, and I don't think many people have that village anymore. As a result, a lot of kids are being raised by TV or the internet, and if you don't want that, you'll find yourself occupied with them almost 100% of the time.
Another issue is that the spouse who stays home can effectively kiss their career goodbye if they spend seven or eight years out of the workforce. Given current divorce rates, that's not a trivial risk.
I wish I had grandparents living nearby, but that's not the case either.
I'm not saying it's impossible - I have two children myself and would probably have had more if I'd started earlier - but it's not easy. And, judging from my admittedly small sample size, it seems to be getting harder.
This varies majorly by child, parent/caretaker, and environment. For instance with my children if we go outside, then they are on full auto mode. They could play in the yard by themselves pretty much all day long as long as at least one parent's nearby watching them. But if we're indoors then they demand full attention. On the other hand somehow our nanny has got them to be able to happily play indoors while she mostly just chills out doing stuff on her phone or whatever - and I have no complaints since it works out great for everybody.