As for my wife and I's decision...
Well for the first five years of our marriage (and the 5 years before that) we'd simply go to work, come home read a book or watch TV. Maybe go out and do some things. Play video games. Sit on the internet and waste time. Ect.
It's fun for a while, but we wanted something more in our lives. Since having a child the last 5 months of my life have been an absolute blur. Kids just provide you with a different adventure, a different learning experience, and new way to find humor and humbleness on almost a daily basis.
You enjoy your free time more when you get it, enjoy your spouse more when you get some free moments together, and just have a much more fulfilling life than before.
Obviously this all changes when they hit the teenage years
It's not a lifestyle for everyone, and it's not even a good one for some people that even do have kids...but it's certainly making my life go a hell of a lot quicker. Which is something that I wasn't feeling pre-kids.