Throwing my hat into the "why is this first" as well. Seeing the archived threads on the topic, clearly this is a contentious issue.
It would be interesting if we took this approach in our home ... pile a bunch of stuff that is "undecided, tbd" at your front door, so that you are forced to step-over and acknowledge the stuff before proceeding to the things you have deliberately sorted. Sure, that approach works well for Stephen Covey & co, but in reality, anyone who lives with a spouse can imagine that it wouldn't last.
Any GTD or Four-D's followers want to chime in?