This is interesting, albeit about South Africa. But the basic idea is this:
Walls are actually making things worse. “No one can see what is happening in
your home so no one can help,” she told the [South African] Daily News.
They keep people from being each other’s natural lookout. And they are an even bigger barrier to social cohesion, in a country that needs it a lot.Further, Marks told Quartz that high walls not only fail to curb crime, they attract criminals—once inside, the criminal is as isolated as the homeowner, free to do as they please.