Why is a high fence built in front of the houses, if it doesn't keep anything in or out?

It's more a matter of privacy from prying eyes than from keeping anything in or out. If you look further, the yards are divided into two parts: a house adjoining and a garden. The adjacent part is also often fenced with a high opaque fence, and the garden either does not have a fence or it is transparent. It is also a question of growing plants which must have enough light.