Jazz basses originally came with 2 concentric pots, which later changed to 3 single pots. The originals had volume/tone for each pickup, while the 1962 to present have volume for neck, volume for bridge, and master tone. I understand that it's a little more complex to have to deal with two tones. Volume/Volume/Tone is simpler. However, Les Pauls have two volumes and two tones. And I'd imagine that you can get a little more tonal variety that way. And if the three knob style is the norm, why don't companies offer double stacked knobs as an option for those looking for a little more control over tone?