Another consideration; it could be the East vs. West thing that I dread to drag in. The east has narrow natural trails, kept ungroom so that bumps will form, some leave areas under the lift line alone while grooming other sections and others seed a bump run. In the natural trails, sometime you don’t have the room to constantly take the slow line down; this can take you dangerously close to the trail edges and the dense woods. I did that one time at Mad River Glen; I ate some wood and was lucky to make it out in one piece. As for the lift lines and seeded bumps, most places leave them 3 to 8 bumps wide for the whole run, sometimes wider if that section bulges out from the narrow corridor. Two areas close to me seeds them 3 to 4 bumps wide in tight formation for the whole run. You start going around the bumps or take the slow line; you will end up out of the bump section (and I believe we agree that once you’re out of the bump section, it’s not bump skiing).
Those wide open bump fields I see in Lito’s book and the galleries from Mary Jane exist at places like Killington and small sections at Okemo, it’s more of an exception in the NE. Could be, we have our share of narrow bump trail/sections that almost forces a zipperline.