Jazzy,
I have a master volume on one of my basses and I absolutely love it. The value of setting up the sounds you're looking for between the neck and bridge is the the first thing I seek, and the master volume, is the last step, before taking sail.
For me, the master volume, is like the rutter on a great ship, that points me in the right direction.
I am more than likely, be adding a master volume on my 76 shorty one of these days; along with serving or replacing my existing pots.
Peace and Love,
Hal-