How can a three-dimensional model of a house be useful to the people constructing the house?
The biggest thing is seeing the depth/spacing of the entire house.
I use to be an engineer in the corporate world. So, we had all kinds of 2-D drawings of all the parts and assemblies we had. However, it really wasn't the 3-D drawings and constructions where we could get a real "feel" of how everything was coming together, going together, etc. For instance, something could be wrong with the drawings. Try to build the model; that flaw would be seen and, thus, be able to be taken care of before the actual thing was built.
For instance, a drawing might show a door to be 4 feet wide. However, once built, it may be shown that the door can't be 4 feet wide, given other conditions like some piping or wiring. If you are building the actual house, you are looking at some drastic and costly modifications. However, if the 3-D model is constructed, then a flaw can be found a lot earlier and, thus, save a lot of money.
It could also give the construction people where they would need to space any outlets, lights, etc., how to space them out in all directions, rather than only approximating on a 2-D drawing.