Why is the standard tuning of 6-string guitars irregular?

The predominance of the interval of the fourth in this scheme is descended from the tuning practice for Baroque lutes. read more

For guitar, the tuning is designed for ease of scales and chords. I personally use some open tunings (DADF#AD) to make open chords easier and provide a new angle on melodies, but that sacrifices the ease of the scales that standard tuning has. read more

If the guitar were designed, like the violin family of instruments, to play primarily only one or two notes at a time then all 4ths tuning would make a lot of sense. The main purpose of lute family instruments, however, was to be able to accompany a vocalist or another instrumentalist in a simpler and more portable format than a keyboard instrument, meaning the emphasis is on playability of chords rather than melody. read more