Two differences I observe now from when I also walked to school through elementary school, and rode public transportation for middle and high school in the Big Bad City:
1) A lot more people were home. There were more 1 income families, and you would see more people out and about during the time one was walking.
2) Strangers were more likely to get involved to protect kids in public. I can recall many incidents of adults, even teenagers, approaching a situation to ascertain if the child was being bothered by a stranger. Even gangs, or those groups thought of as "radicals" had a "moral code" that young children were off limits and would protect them if they thought they would be bothered.
+ This summary nails it.