Let's assume you're structural engineer or modeller in the firm that designs framed or modular buildings. Most of the work is done in BIM applications these days to coordinate the design and solve all nasty problems in software rather than in field.
Modelling is not an easy job to do, there are a lot of thoughts around the smallest elements in a project depending on what detail level a designer tries to achieve. More detail pays off, as the building is being constructed for the first in the computer (with all related problems), and for the second time, building it in reality these problems have already been solved. On the other side it is a very time consuming work and might take as much as real construction if not thought through.
BIM software such as Autodesk® Revit® allows all designers to be at one page and realize their decisions in a model. It lets a designer to be capable of modelling in such detail that every part or element might be in a model. But if not automated it can become a nightmare. So helpers are crucial to get things done quickly.