This is the question to which one constant answer is "If you need to ask, you wouldn't understand", which is not addressed to the music of the blues but the condition. It helps to keep in sight that in its roots blues was music generated by an condition -- having the blues. The condition is similar but I would argue different from classic depression. But the blues instead of generating analytical polysyllables and pharmacutical fortunes, generated music. I genuinely think it might be best left not further analyzed (the condition).

The roots of the music are that it was the music generated by that condition.