Depends on where you live. In Japan, most of the time it’s either way too hot to hang out on the balcony or way too cold. In Europe it’s fine in many places for most of the year.

Some of it also has to do with rent prices which can be higher if you have a balcony.

Also, and again in Japan: There is an emergency balcony exit in some apartment buildings in case a natural disaster hits. It’s probably easier to climb your way down a bunch of balconies with holes in the ground than a blank wall