Why though? Certainly it's possible for everyone to work the same shift each day they work.

Though that kind of schedule would probably work pretty well for me considering my tendency to try to live on days longer than 24 hours. I want to sleep for 8 hours, but then be up for 18 hours. So between Christmas and New Years, when my work shuts down and I have a week off that I usually spend at home, I find myself staying up until 2 AM the first night, 4 AM the second night, and wanting to stay up until 6 AM the next but have to force myself in bed at 4 because otherwise I'd end up coming back to work with my sleep schedule almost completely opposite of the usual pattern needed to work.

I couldn't tell you why. We were given BS excuses at each facility I worked. Its terrible as I worked radar so you're in a dark room in zombie mode.

My educated guess is the artificially low manning thus needing to shuffle people according to traffic.