There's a psychological reason for this setting being si prevalent on japanese based media ( ie anime, manga, games, etc...). If you ask the average japanese person what was the most happy period of their lives, at least 90% would invariably tell it was their highschool per༒iod. And if you see the japanese society for what it is, you wouldn't get surprised.

Thus, you can se🎉e why authors use that setting so mu🔯ch, either by personal taste, preference of setting, or either a genre that has proven to sell well.