Modern Blues has it’s roots in the tribal songs of the west coast of Africa among others. These work songs were used to keep good morale during the work day and the rhythmic bass lines and rhythms from the traditions of the villages would keep them to a steady pace.
When the music landed on the shores of the United States, it slowly evolved into two distinct styles, Gospel and Blues .
One side was the good, clean ,god fearing, hard working face of the coin. The other was the late night drinking, dirty dancing, secretive face of the coin. The first celebrating the lord and giving prayer. The latter, bitching and moaning about your boss working you too hard or you wife not paying you enough attention.
The funny thing is that these two very contrasting styles, were mostly played by the same people. Musicians in the black community in the south at the time were few and far between, so lots of blues musicians used to play whatever would pay the bills. We should also remember that way back to the origin of the Blues, the most influential blues-men of the time had been preachers or very religious.
The interesting thing about this evolution of the music is that it changed to suit the climate that it arrived in. It took influences from whoever it came into contact with. The blues has adapted to whichever place it landed. But it has always remained the music of the people. It still serves essentially the same purpose as it did in West Africa, to celebrate life and bring to light the troubles of the day, but most importantly to bring people together to have a good time.