From my experience, there are different cultural aspects to privacy and sometimes, simple metal bars balconies are fitted with fabric to hide what's happening inside the apartment from the outside world.

I guess in many places where this is more culturally predominant, they install solid barriers on those balconies.

Usually those barriers leave a gap at the bottom for water and debris.

https://www.berlin.de/en/news/8025956-5559700-solar-power-ba...