Traffic and lack of walkability is definitely an issue (and not only for kids, btw). I am wondering if the idea that children must always be within arm's reach

Traffic and lack of walkability is definitely an issue (and not only for kids, btw). I am wondering if the idea that children must always be within arm's reach of an adult, has in a way contributed to building cities in a way such that there is no (safe) walkability in many places?