Why is the guitar tuned the way it is?
To make a long story short, the guitar strings are tuned 5 frets apart (except for the B string). As you move up the frets the pitch increases by semi-tone increments. To play the chromatic scale you go up four frets and then move to the next string.
This allows you to place your fingers along the frets, one finger per fret, in what we might call the “classic position”. The tuning of the guitar is based on this idea. It allows you to play up to two octaves of popular scales in the open position without moving your hand from the classic setup.
In other words it is tuned to take advantage of the four finger classic setup.