I agree with you, but that's the point, accidents can happen anytime regardless if you are with your child or not.
But, as an adult, you'll have a different reaction than a child and you can save his life. For example, seeing ahead that there's a car with engine on and being aware of that car. Reacting faster than a child once the car starts moving, pushing him away and saving his life. There's different scenarios where an adult reaction is different than a child reaction and can save a child life.
I gave this article as an example, that if this kind of accidents can happen with a 10 year old, on the pavement, with friends next to her, then why would anyone ever consider to let a 7 year old walk on his own to and from school?
I also speak from my own experience, as a child who walked to and from school since the age of 7. I had to take a bus and it was a 30mins journey. It was child neglect, even if my parents don't think so. I had a lot of dangerous situations as a child. It's a miracle I'm still alive today, despite everything what happened to me during my childhood. It's not only about crossing the road and being hit by a car, there's so many other things which can happen with a child while walking on his own.
There's plenty of time ahead for a 7 year old to learn how to be independent and walk on his own. I see no reason why parents will push a kid to grow up faster, other than if the parents don't care and actually neglect their own child.