Calligraphy pays attention to "heaven and earth left and right", which means leaving space appropriately. Otherwise, it would be called standing upright.
This is very particular. Generally, the vertical banners are narrow on the left and right and wide on the sky and the ground. The banners are the opposite. The fans have almost the same space, the album pages have less space, and some cursive scripts leave no space or some leave space.
There is no rule in leaving spaces blank, and it depends on the actual combination of text. It only needs to be harmonious and consistent with the aesthetics of calligraphy.