Does anybody know why A&P stopped doing random systems and instead are using a four-year system?
I believe that they have been trying to make every event rotation much more organized in recent years. I'm not entirely sure of the reason, but it's not unique to A&P.
The yearly systems typically relate to each other in some way rather than the haphazard grouping seen in previous years. It also prevents the possibility of the same system being tested multiple years in a row (*cough cough integumentary 2014-2016*)
Under the old format, only one system would be replaced each year, so each system would get 2 years of run in B division and 3 years of run in C division. They changed it so every system is replaced each year around the same time that B division went from two systems to three.