From Stack Exchange - Music:
… one of the reasons guitar became so popular in western culture in the early days, is because its portable.
So it’s sort of a travelling minstrel’s piano. During the late 19th/early 20th centuries in America (post emancipation act), there were lots of travelling musicians who couldn’t afford a piano; and even if they could, they couldn’t have carried one since most of their travelling was done on foot, they would literally play for a couple of meals and a night under a roof. These are the guys that brought us the earliest forms of blues, like the Delta blues; which were basically the old slave work songs Blues’d up (call and response etc.).
If you scout around you can find old photos of these guys with the most battered looking old instruments you can imagine.
However you want to look at it (poor man’s piano/portable piano), the portability and relative cheapness (guys would knock them together out of bits of random wood), is a major difference which helped start the wheel of popular music/culture rolling.