That might be a reason:
In 2002 I was researching the aims and motivations of business managers and designers and found them to be rather different. I also found that there is an overlap which is a "natural" starting point for a constructive conversation between the disciplines.
Since some time the design management discourse is increasingly assuming that all design has to be simply subordinated to the aims of business management (the left part of the diagram above). At the same time, values not intrinsic to business (the right part of the diagram) have been increasingly squeezed out.
This lack of non-business values is exactly what social and environmental activists criticize. Design would be ideally positioned to introduce just that.
Alas, that won't happen as long as the current discourse in the discipline of design management itself does not recognize that there is more to design management than management alone: There is also design in it.