Some trivia:
His "signature sound" on the guitar did not come out of ego, it came out of necessity. He tried to work the bottlenecks and slides the traditional way, but his fingers were so fat that he couldn't make it work. He came up with something to approximate it by wiggling his fingers on the frets (creating a vibrato).
He grew up on a cotton plantation, working the fields and playing the guitar in his free time. The white plantation owner taught him how to drive a tractor, and tractor drivers were making 10 times more than the cotton pickers. When World War II broke out, he enlisted in the army and was getting ready to be sent overseas when the army found out he drove a tractor. They immediately discharged him because a tractor driver was considered a civilian occupation that was "vital to the war effort".
He played the blues because, growing up in the 1930's, he would stand on the street corner every Saturday afternoon and play gospel songs, and everybody would compliment him but not leave and tips. When people asked for blues songs, he would play them and leave tips.