How come in computer games/films you cannot easily see what is above or below you?

In computer games, in first person, you cannot see what is above you and below you, like you can in real life. how come this is the case?

Does it have to do with the roundness of your eyes or something? it cannot be the size of the screen, because even on very big screens this is the case. does it have something to do with the camera, and the wat it is positioned? or that you have 2 eyes and there is only one camera?How come in computer games/films you cannot easily see what is above or below you?
depends on how you program the game....How come in computer games/films you cannot easily see what is above or below you?
May just be the computer game, or the camera itself. Maybe the software . Computers are very complicated.