I have worked in Truck and Car, and it is done that way for fit location.
Every part peice is dimensiond frome the center line of the part no mater what the shape or if their is a feature or not.
I like feature to feature, and fit to fit dimensions to check tolerence of fit to the next part...
We have a senior designer that dimensions parts with a theoretical starting point and dimensions from a 0,0,0 from the center of a part and dimensions everything off the theoretical center line. Is this wrong? No features to dimension from. I think this is the poorest dimensioning that I have...
We have a person here (a Senior Designer) that dimensions from a theoretical datum in the center of the part and uses the coordinate system. I think this is way wrong. I think that coordinate dimensioning is an easy way out of dimensioning correctly.