This is for the projects that (for whatever reason) cannot or will not be fully modeled automatically.
When hand edits are necessary, the cross sections become useless for any future processing (earthwork and probably annotation). Allowing a set of cross sections to be edited by hand, then using those sections to generate a corridor model, may allow edited sections to still be useful to the project. Perhaps something that could "read" elements like old Geopak earthwork processing - These Elements on These Levels represent my components, and just apply a linear transition between one section and the next.
I understand that would not be as accurate as a thoroughly modeled corridor. It would allow corridors to be modeled to a certain percentage completion then hand edited for specific details, yet still be useful by the design software in some form after those edits.