Another observation.
As we naturally see more in a rectangular field rather than a squarish one. perhaps widescreen imitates our natural field of view more than 4x3 screens.
Widescreen also introduces a whole new dynamic into setting up scenes in Poser, and it's not just more room at the edges, but it greatly affects the entire composition process. You are made to think about how to use your new workspace in a completely different ratio. It was quite a  new thought process for me.