As chris says, many people have extremely strange habits when they are using their computers. I've seen people sat really close, hunched over their keyboards, I've seen people holding their mouse, hovering it over the mat (like an overhead crane!). I've seen monitors placed directly on a desk (which is generally waist height - I think, if I could find my waist...) & I've seen setups where the keyboard & monitor at at 90 degrees so the user has to twist their body! I've seen instances where the IT dept has abandoned a working computer on a desk & the user has simply sat on a chair & got o with it - not bothering to move anything to suit them, not even bothering to adjust the height/angle etc of the chair.
I wonder if these same people would drive their cars in the same fashion - oh, hang on, some do.
They cling to the wheel for grim death, hands at five to one & practically biting the wheel as they stare over the top or their seat is fully back, forcing them to hold their arms out straight...