Yup, each to his own. In my experience, flatter boards certainly facilitate speed, dexterity and string bending, partly because they allow a lower action. And I can definitely believe that a lot of bass design is "because we've always done it that way". But for the technique I referred to as "digging in and boogieing", where you are really pulling hard at the strings with the right hand, you don't want a low action (or, more accurately, I don't want a low action), particularly on E and A, because the damn things keep bouncing off the frets and you have less tension. You'll be gripping quite hard with the left hand as well, and I find a cambered board facilitates this. It's more comfortable. This is not a sophisticated way of playing, but it's great fun and conveys a sense of drive and urgency.
FWIW my current bass is very flat.