The way a guitar is tuned can be said to be an accident of evolution. There was no standardized pitch until the 1700's, and there were many different guitar-like instruments around before and after then, all unique but similar.
The Modern Day guitar grew out of the lute, an instrument used over 400 years ago. It was tuned to a very high A, with anywhere between 12 and 20 strings, in pairs of two. Another precursor was the Cittern, with 5 sets of two strings tuned to fifths. You can only find these in collectible shops now.
The real modern classical guitar was standardized in the late 1800's, and through the need for a common tuning, the concert tuning for guitars was established for it, for no real specific reason except perhaps it blended well with other instruments, and was universallly playable and ultimately accepted.
Also, it did enable the playing of all chords in the first position, and helped establish a way to make the instrument uniform in the way most other instruments were. Even the old guitar like instruments had their own styles, different number combinations of strings, and different tunings that were accepted as standard for that instrument.
The modern day guitar evolved, and became a standard. Not a lot of complex pre- thought out theory went into exactly how to set it up, it just became that way through the ages to conform with other instruments and still remain playable.
Perfesser Bushice
