Depends on where they came from, which group in society they belonged to. If you take the European guitarists, they used the standard classisist tuning on the six string normal sized guitar.
If you take the black Blues guitarists in USA. Well, then you get a whole different ballgame. They tuned their guitars so that the strings suited they're way of singing and playing. Suited their musical intent. They often tuned in open chord tunings. Open D, E or G. Some used 5 strings. Some played slide, using a knife, a screwdriver or a bottle, or whatever they had. Anything that sounded good. There are so many ways to tune a guitar. And one shouldn't be scared of experimenting. If it sounds good it's alright.
One must remember that it's the emotional expression that counts. If you can move your audience with a song. Well, then you are doing it right. No matter how you tune your guitar. The standards have been invented to make it easier for guitarists to play in orchestras, and vice versa. But to really become a great guitarist one must find ones own true musical voice at some point. And when you're there… an alternate tuning is something you pull out of your toolbox. Or a special tuning that you invent along the way and write some songs on. The more skilled you get, the freer you can be in your playing and tuning.
