Official Luthiers Forum!

The two hands are performing different tasks. The picking hand needs wider string spacing to pick individual strings cleanly. Even a 2 1/8" nut will have string spacing equivalent to the narrowest bridge spacings used, and with a constant width neck and equal spaced strings you have the problem of pushing the outer strings off the edge of the neck....which is worst at the midpoint of the string.
Production guitars are designed for the 'average' player....and those preferences have been developed over centuries of playing.

Different playing style. Playing closed chords up the neck with the thumb over the bass string is seldom done on a classical. I can barely do it (my hand span is 21.5 cm), but it is painful.

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John