Reason is the Mode of Transportation

For once, Erza Klein makes a good point in the pedestrian-cyclist vs. driver argument. One of the major inhibitors to walking in a city like Dallas is that everything is too spread out. This isn't to say the city completely lacks walkable areas (Lower Greenville, Uptown, Downtown) but that most of the city planning has gone into building a road infrastructure that inclines people to drive versus walking. The bus system here is a lovely mess; although the growing light rail lines are making things easier for some. But when you have a two mile stretch of river crisscrossed by two and three lane bridges for vehicle traffic and only two rail bridges (one of which is for commercial traffic) then obviously the city planners did not have a rail system in mind. As I said, Dallas is walkable to a degree, but even then you still need a car to enjoy going to the better places in Dallas and not settling for what's within foot-distance. Cities like Irivine, CA are much the same as walking isn't sensible. This isn't about being good or bad to the environment, but about what's the more reasonable way to travel.
I'm now going to hit myself for saying that Klein has a good point.