Architects are not the only people who draw 1:1 and not at 1/12 scale.
The thing I have always found interesting is how other programs (like Microstation) use a full scale and you usually have to scale down by 1/12 when importing a dgn.
As for the question I think it goes back to the old scale up scale down by 1/12 to get things into your scale if you work in another dicipline.
R10 - 2020 ACAD
2008 - 2020 Civil 3D
2014 - 2020 Plant 3D
2014 - 2020 Revit
V8i - V8i SS4 Microstation
Infraworks
2018-2020 Inventor
2020 Navisworks