Several experts talk about the issues with many fewer American kids walking to school compared to fifty years ago. The negative effects? Less exercise, less learning about active transportation, less exploration in and knowledge of their own neighborhoods.
I suspect many people will blame parents and kids for this and tell them to simply walk and stop being lazy/decadent/unnecessarily scared/etc. However, it is not as if many Americans regularly walk places outside of major cities and denser neighborhoods. Some of this may be due to comfort but other factors are involved including nicer vehicles, more fear about crime, more sprawl (particularly in the Sunbelt) which means further distances and fewer pedestrian-friendly streets, less emphasis on physical activity in daily life (which is not necessarily laziness but rather more sedentary lives overall), and a shift toward technology (starting with television) rather than active exploration. In other words, this is likely a multifacted problem that is not easily solved by simply “making” kids walk.