system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: how we ended up using a "standard" tuning on guitar?

When did it became "the norm", what led us to adopt it, also why the B string is not a C to keep the same intervals as the other strings?+
gpt
As you have noted the guitar is mostly tuned in 4ths, with a major 3rd between the G and B string.

The advantage to tuning in fourths is that it makes it easier to play melodies across the fret board. But it also makes it harder to play chords. By switching to a major 3rd interval the notes on the higher strings come down a fret making it easier to reach for forming chords.

If the guitar was all fourths it would be EADGCF -- the problem here is that barre chords would be tough, because you have a minor 2nd between the low string and high string which doesn't sound well. So you would have to compensate with fingering and lose the ease of being able to slide a barre up and down the neck.