Well, its not just guitars but simple stringed instruments that can be easially played... There are drawings from the American Civil War of simple stringed instruments using cigar boxes as sound boxes being played in various camps... The guitar is a logical choice in that it is has a fuller sound than a violin, mandolin or banjo so "folk music" being what it is there is really no other instrument that would have been as universally appealing than a guitar...

MO, of course...

B~