While windows remain an accepted part of aircraft design, they have since been kept as small as possible. These days they are typically 33 centimetres high. The panes are contained in a window unit which is fastened and sealed to the aircraft structure. It is, of course, much heavier and costlier than the thin sheet of aluminium it replaces, and the structure of the aircraft needs to be reinforced to support it. All this extra weight means fewer passengers or less cargo can be carried, so it reduces airlines' potential revenues.
Windows also present a maintenance problem.
The position of the windows varies depending on the aircraft but generally designers try to place them with their centre line a little below the eye level of seated passengers. On the ground this is perhaps too low, but in flight it gives an oblique view of the ground. Little would be gained by positioning the window higher. Because the seats are placed at the widest part of the circular or oval fuselage, the windows would end up angled upwards some 10 or 15 degrees. The only view the passenger would then have in flight would be of the sky.