Why Is The Guitar Tuned The Way It Is?

[V7#5b9]

Andrew Wasson delivers the formal explanation. The first 5 minutes of the video provide the essence, the rest is just promotional stuff. 

The second video is interesting because it provides correct observations with regard to the standard tuning itself. However, I know nothing about Eric Blackmon, and I wouldn’t call his explanation a formal one. In my mind it does not qualify as the correct one, but it does serve as a good supplement. Apparently, YouTube does not allow embedding of this video, so you will have to use the link itself. 

https://youtu.be/5hc7OJqQYaA

Edited November 8, 2018 by V7#5b9

[DianeB]

That was a fair, if not fully satisfying, answer. I suspect that if a guitar is tuned fully to perfect fourths, five- and six-string chords become difficult to finger. A demonstration would have been revealing. The human hand seems to demand a major third in there somewhere to get the harmonics. If your style doesn’t demand those big chords, a la Stanley Jordan, go for it and crank up those B and E strings! Recovering banjo player Carl Kress tuned in perfect fifths.

[V7#5b9]

@DianeB, 

If you are interested, the following article by Howard Morgen gives additional insights with regard to the guitar’s irregular, unequal standard tuning. 

Fingerboard Insights For All Guitarists 

[Dave White]

@V7#5b9 - thanks for posting!

[FThomas]

And that is what makes the chords:  E   A   D

The exact same construction - Root 5 Root 3

[NeilES335]

10 hours ago, FThomas said:

And that is what makes the chords:  E   A   D

The exact same construction - Root 5 Root 3

They are all major triads.

[FThomas]

1 minute ago, NeilES335 said:

They are all major triads.

C, E and G are all major triads as well.

G is R 3 5 R 3 R

C is X R 3 5 R 3

F is X X R 3 5 R

It is not that they are all major triads, which they are, but it is that when moved to higher strings you must raise the 2nd string 1 semitone and when going the other direction you must lower the 3rd string one semitone.  The above, like E, A & D have the same chord construction even though the chord shape is different because of the Major 3rd between the 3rd and 2nd strings instead of the Perfect 4th and all the other strings to include between the 2nd and 1st strings.  

It is for that reason that understanding the layout of the fingerboard can be a challenge.  Once you understand it can unlock a lot of mystery.

[V7#5b9]

It is rather difficult to explain all the benefits of fretboard visualization techniques in a simple post. As the above-mentioned article alludes, it’s highly unlikely that any beginner would realize that the E, A, and D are identical in construction and voicing. But, this is only the tip of the iceberg.

CAGED system is one such technique, but it depends on how far one is willing to take it. Learning shapes without studying their anatomy, may or may not be enough, depending on the players goals.

Learning chord shapes, formulas, intervals, spellings, etc., is part of the deal. Beginner courses don’t even mention how visualizing the fretboard from the perspective of string sets can enhance your understanding of it. And there’s so much more …

[John Wells]

Actuallly it began as five strings tuned ADGBE. Here's Fender's article on how it came to be. Lotsa luck.

https://www.fender.com/articles/tech-talk/standard-tuning-how-eadgbe-came-to-be