Parking structures don't drive families out of cities, the high cost of city housing, lack of back yards, perceived higher crime, and need to transport kids all around all do. Its simply faster and easier to take kids from school to piano lessons, and then to karate in a SUV in the burbs than on various bus and subway routes
I've lived in the city (Beacon Hill) and in the suburbs (Melrose) with a child. In the city, leaving with baby/child was as simple as walking out the door. The day's shopping took about an hour to get groceries, booze, dry cleaning, etc. In the suburbs, the day's shopping takes about 3-4 hours, mainly due to the time required to drive around. Lack of a yard, parking inconvenience, desire to own a home, desire for more space drove the move to the 'burbs.
Long story short, after 5 years, we're preparing to move back to the city next summer. I'd be more than happy to outline the pros/cons of raising a kid in one environment or the other, but for the sake of brevity I'll just say that the "quality of life" scales tip heavily towards the city. Everyone wants different things from life, but from my family's perspective, the city is where it's at.