Well, there is this scenario. I take a picture with the stock camera. I then can use stock app Gallery to view those pictures, but in 4.3 I could also use QuickPic. If I wanted to tweak one of those pictures to make a background image, I could also use the Blur app. With 4.4, it sounds like I would need to duplicate the original picture folder that Gallery used, 2 more times for QuickPic and Blur. Same thing if I wanted to look at movies, I could use the stock Video app, but I may prefer to use MX Player Pro. For music I have the stock Music app, Double Twist or PowerAmp.
Why would I have so many apps? Frankly with the $50 promotion for my Note 3, and another $50 for my tablet, I was encouraged to try a bunch of apps. And in the uncommon chance that one of those apps had a bug, I could use one of the other apps in the interim.
The sky isn't falling. The chemistry of the sky has changed, to something that's said to be more secure, but it discourages the use of the external card and hampers flexibility. I would call this an extreme change in how Android operates, and one either conforms to the new restrictions, or is forced to do something that is likely to void the warranty. I can agree that there are people out there, who really need to be protected from malicious apps accessing folders improperly, but to me this feels like universal parental controls.
Even heavy handed Apple didn't force me to update the OS on any of my previous phones, if I was happy enough with how they were, as is.