Why different scale forms?

[SunnyDee]

We've been talking about scales and their importance for different types of guitar players in another thread.

I have a specific question about the forms of the scales that beginners seem to be taught:

I'm talking about when they are taught to play one note at a time from the tonic through 2 octaves, no open strings.

In beginner classical guitar, the first scale is almost always the major and the shift from the first octave to the second is horizontal, shifting on the "do" or tonic up the neck moving across 8 frets.

In beginner acoustic/electric, I know why they tend to focus first on pentatonic, but the question is, why do they tend to shift vertically into the second octave rather than horizontally so that the scale is all practiced in one position, staying within 4 frets?

Opinions about this different use for the second octave?

[rick-slo]

Do you want open strings as part of your scale? Do you want to exploit the general sound difference of the same note played on different strings? What is the harmony that may accompany the scale? etc.