I use volume often for calculating weight of fixtures, EOAT robot, etc.
I knew a mold shop estimator that would open the molds in cad and use the volume differences from stock to finish part for roughing estimates and different groups of surface areas for estimating finishing time. He was pretty good at estimating.
At first I was appalled that someone wouldn't know the value of having volume and surface area analysis in CAD software.
But I'm going to give you the benefit of the doubt, as I suspect this is just a poorly worded question. What you're really asking is why these numbers are showing up in your CAM dialog boxes, and how they can be used in the context of generating toolpaths in CAM. Without knowing more, it could have to do with MRR and 3D finishing cycle times.
You'll need to put some more effort into your question if you want a real answer. Post a screen grab. Ask specifics. Lazy questions get lazy answers.