I hate that site. I really do. And now the Zillow and a other realty sites now tap into it really ticks me off. The only areas that are really favored are large cities or dense commercial areas in suburbs. There is no love for those who choose to live the rural or exurbian life. Of course those area's aren't "walkable." The whole point of getting away from people is to litterally put as much distance away from the headaches and traffic of the busier parts of town. Give me a community with a low "walkable" score any day of the week.
Could be a quirk of my city, but where I live, it's suburbia that has the worst traffic. In the walkable inner city, the traffic gets dispursed onto many gridded streets and flows well. In the unwalkable suburbs, all the traffic gets forced onto very few, main commercial arteries, which are endless streches of traffic and strip malls.