optics - Why do things that are far away seem smaller?

As you see things that are far smaller, a funny question about this:

Imagine there are many people in a row (all are same height)

    A            Other Guy B             C             D
    |                        
you |  distance     |        distance        distance 
    | <-------->    |        <------->   |  <------->   
    |               |                    |             |

    |               |                    |             |
    ------------------------------------------------------  floor   

From your point of View you see D much smaller than you, then.. Remember, if this is an "effect" then D is not smaller than you, it's just far away (and this is not earth curvature, because D is smaller in all sense not only in height)

so..

Imagine you have a laser pointer and want to point your partner's face to annoy him so how do you target it? do you align the laser with the floor at the height of your own face believing in geometry? or do you point directly at the "little person" D ?

    A               B                    C             D
    |. . . . Laser path . . . . .  . >. . . . . . >. . . . . . >. . .  . >
    |  ^            |                           
you |  |parallel    |                    |

    |  |            |                    |             |     
    |  v            |                    |             |
    ------------------------------------------------------ floor   

Then you don't hit him, and the "visual effect" became so real that you start to think D is for Dwarf.

There is something Wrong? Physics opinions are welcome!

I think the answer is that floor itself will seem not aligned eigther so targeting the Dwarf you will be really aligned with floor because floor itself will have perspective effect.

    A               B                    C             D
    |. . . . Laser path . . .   
    |               |        ''''''''''''......

you |               |                    |      ......>|
    |               |                    |      _______|___floor   
    |               |         ___________|------                        
    --------------------------

Anyway its weird