What is the point of changing or removing longstanding functionality?

Many professional Adobe users eventually find themselves functioning in the programs by muscle memory - you do the same tasks so often that you stop thinking, it becomes a flow. And then Adobe updates the program and suddenly, for example, shift no longer constrains proportions. A way of working youve become accustomed to over years is different, out of nowhere, for no clear reason. "You can revert to the old fucntionality in preferences" is not a good response, and proves there was no need for the change. Want to save as a PNG, as youve done 20x per day forever? Nah, we REMOVED save-as options! If you need them back you can use the legacy save-as! 

NO! Let me keep working the way I have as the default.

And speaking of shift-proportion-constraint: all other Adobe apps still have the same functionality. So when switching between AI and PS, shift does one thing in one app but not the same thing in the other. How is this good?