The same dynamic that results in zoning that prohibits food trucks also results in large swathes of residential area in suburbs with no real restaurant options inside walking distance.
I would expect that food trucks would naturally stay away from such areas due to economics, anyway. You need to draw a lot of people, and there aren't a lot of people who are going to travel to visit a specific food truck, so you need passersby which means you need density and activity.
Suburbs almost by definition have very little that's walking distance. One house per family makes everything very spread out and far away - in exchange for everyone having a lawn and a backyard that's 'theirs'.
Many suburbs aren't like that though -- they are just parts of a city that are outside official city limits and not those sterile "Stepford Wives" dystopias. I live in a suburb of Washington DC that is basically as dense as the the city itself and full of apartment buildings, restaurants, bars, and Metro station all within walking distance.
