Screens are visual, and human vision is biased to search lateral space over vertical space. This is due to the nature of humans' visuospatial limitations. We're largely 2d animals in our movement: front/back & left/right, not so much up down. This is different from animals like birds and fish who constantly have to navigate all 3 dimensions to catch prey and avoid death. We aren't ignorant of vertical space, but hori…
The other one is internal real estate. Wide screens mean wider keyboards and larger batteries.