Because only babies and crazy people get to pretend that reality actually changes when you close your eyes and hum. And, reality is the thing that priorities hang on. If you think you can change it by taxonomies and meetings, you still have only two arms, only now you’re also screwed.
Google defines priority as (wait, since when did Google define anything?): If something is a priority, it is the most important thing you have to do or deal with, or must be done or dealt with before everything else you have to do. [Ref]
Root: Middle English priorite, from Old French, from Medieval Latin priōritās, from Latin prior, first. [Ref]
Interesting note: “Prioritize” is a Bushism before we had Bush! “Prioritize is first recorded 1973, apparently coined during the 1972 U.S. presidential election.” [Ref]