Another major factor you didn't mention is urban housing prices. Before kids, we lived near downtown Seattle in a walkable, urban neighborhood. It was great, and is where I would have preferred to stay long-term. When we decided to have kids, we knew that buying a large condo or decent-sized detached home within the Seattle city limits would be way out of our price range (housing prices in Seattle have almost reached San Francisco/Silicon Valley level).

So we moved out to the burbs, where we could afford a starter home big enough for our two kids and a mother-in-law.