Yeah, I think the issue is that once you've finished designing an interface or your software is feature complete, the company is faced with a problem: You don't have any actual work, but you absolutely need to maintain your expertise and sales.
What features can you really add to Excel at this point? What do you do when your market analysis says your application and interface are about the best they can possibly be? What do you do with your engineers when your product is, by nearly all measures, complete?
This is the problem that Google search has. And Microsoft's Windows and Office teams. We had basically everything on lock for quite awhile. Changes now are seldom improvements. They're just changes to justify the engineers' salaries that the company has to keep paying because maintaining that is a core competency. Moving all of them to a new project spoils your expertise in your own product so you can't just do that.
At this point, UX design for these products should probably shift to aesthetics, much like the auto industry did. And that's largely exactly what Windows has been since Windows 7. Aesthetic changes.