This is a question i ask time and time again and no one is able to answer it.
Why to learn more than one scale positions (boxes) on the guitar? Every box sounds exactly the same!
People say i can transfer it. But so what! They are moveable. So instead of playing the first then the second position, i could play the first and move it and play it again... Right?
Each position is 12 frets away from its exact repeat. So if you don't learn any of the positions in between you are not able to play on the majority of the neck for a particular key.
For instance, if you are playing G major, and you only learn the "first" shape:
-------------------------0-2-3-
-------------------0-1-3-------
---------------0-2-------------
---------0-2-4-----------------
---0-2-3-----------------------
-3-----------------------------
Then you have no scale pattern to play from there until the 12th fret, where you can play the same shape:
-------------------------------------12-14-15-
----------------------------12-13-15----------
----------------------12-14-------------------
-------------12-14-16-------------------------
----12-14-15----------------------------------
-15-------------------------------------------
If you're playing a D barre chord using the 5th and 7th frets, it might really help to be able to get right to your G major scale without having to move several frets away:
-----------------------------5-
-----------------------5-7-8---
-----------------4-5-7---------
-----------4-5-7---------------
-------5-7---------------------
-5-7-8-------------------------
Note that the last scale plays the notes of the G major scale but starts and ends on A, so it might sound a bit weird to play it just like that. The point is you could get to G major notes right in the middle of the neck if you need to as long as you know where those notes are. That's what learning the other scale patterns is good for.
Adding to Todd's answer - they don't all sound the same. Or they shouldn't. The notes will have the same pitch, but some are played on different strings, so they will sound different.There's also the propensity on guitar to bend some notes: which may be played with a 'wrong' finger in some positions; also being able to slide up and down, and hammer /pull off, between certain notes is denied when you only know one position.
Then there's the state you get into when you're widdling in a solo and you reach the highest note in the one box you learned. What then if you want to go higher? Keep sliding up the top string? That's what amateurs do. Move up a box or two, and you have extra notes under your hand, meaning you can play lower without all that sliding.
Personally I prefer whole scale patterns, as in starting and finishing on a key note, which shrinks the number of notes available somewhat, but being aware of the 'extra' notes lower and higher helps with solos. The other point here is that we stray into modal territory. Take the standard A scale in first position (start on 6th string 5th fret and use frets 4 to 7, so using all fingers) Some people will start from the 6th string 4th fret (G#) so effectively will not be playing A major, but instead G# Locrian. If you're ready to think in this way, fine, although starting in G# Locrian which then morphs into B Dorian doesn't help a lot.
