EddyC - with respect (and I mean it) I don't think you understand the vast difference between the ME drawings you describe, and a set of structural drawings, say, for a building.
You are, in my humble opinion, comparing apples to existentialism.
Your drawings are used in a particular context, or culture, of fabrication where there is no "in-between" entity between the designer and the fabricator. Thus, the ME drawings you refer to MUST be precise because the culture in which they are used, and the kind of "thing" you are producing demand it.
For structural designs, the level of detail of locating each hole in a beam, determining how long a column is between connection plates, etc. is not required on our plans because the process of creating that beam or column is performed in a vastly different community or culture. The information is there, and is shown on the 100% structural plans via dimensions, notes, references to industry standards. A steel fabricator, or a formwork designer picks up the structural plans and works through them, adding value from their own expertise, to provide the necessary (and adequate) level of precision.
In other words, this vast community, or culture of structural engineering/fabrication/construction negates the requirement for the kind of precision that you require in your ME world.
One isn't better than the other...just different.
There is also a vast amount of calculations, analysis, and constructability that goes into a set of structural plans that is essentially "hidden" from those who don't know structural engineering but which are "in the plans" none-the-less.