Or is it just the ones who do who are being filmed performing music? It's just that it's being shown as a norm, like "everyone" is singing to each other.
I'm pretty sure most flats in the UK don't have balconies. I certainly don't have one. I feel like there's this unrealistic message that people spreading, that we just need to wave at each other from our balconies and all will be well and we'll have instant camaraderie.