I think ultimately the reason she used bass is not important. She obviously liked it or she would not have continued. What I do believe to be important is the quality and consistency of her recordings. She was an extraordinary artist. There is no contesting that. She's done a plethora of recordings both as a leader and a sideperson that have endured the test of time, many of which are considered a mainstay in anyones jazz collection. She was one funky organist with an immediately identifiable sound and I'm just glad she existed long enough to bless us with her gift!