All Fourths Tuning (E.A.D.G.C.F)

The All Fourths tuning is the closest regular tuning to the standard EBGDAE. Given the ease of remembering chord formations in regular tunings, why does tradition tune the highest two strings down a half step?

One reason may be the distinct lack of full six string major and minor chords in the All Fourths tuning, even in open position. There are, however, numerous easy-to-finger four and five string chords which can be moved readily around the fretboard.

All chords and scales from the low four strings of standard tuning can be used verbatim, and they can be transposed directly onto the upper two strings. Electric bass players often find this one of the easiest guitar tunings to use, since it is a very simple way to extend the tuning of the four string bass to a six string setting.