Because in this specific case they are the only party who did anything helpful to the people who were trying to turn money into a road.

I don't think he meant that you have to do labor to add value.

^^^

Perhaps because they are the ones that actually convert the plans and raw resources into a useful building? Plans for bathrooms and buildings can be easily pulled from a shelf of existing plans, tweaked a bit, and sent out, but building the actual structure can never be avoided.

Tell me you don’t know anything about construction without telling me you don’t know anything about construction

Mission accomplished. I never stated anything about my knowledge of construction. However, for whatever little it’s worth, I do know more about it than most people I encounter, especially in a forum like HN.