Well, they are Autodesk and it is their program....
In the 2009 release, they tried to minimize the need for command-type Aec Content files running custom routines by creating special tools that could do the same without having the tool run an Aec Content file.
So they created a tool that replicates the old Aec Content fire-resistance-rated polyline routine.
They also added a generic command tool that has a layer key - so if you are looking to create a tool palette tool that draws a polyline on a particular layer, based on a layer key, without the need to select walls as the defining geometry, you might want to look into that. The custom command string could simply be the PLINE command, or you might write a simple LISP routine that collected the start point and width (or perhaps calculates the width?) and then starts up the PLINE command, feeds it the start point, sets the width, and then leave the user to enter the rest of the points for the polyline. The layer keying should kick in after the command is terminated - but you may want to test that just to be certain.
Using ADT 2004 at work; access to 2005-2009 at home
I can think of very few situations where a global pline with setting other than 0 would be useful (to me anyway). Wouldn't it be very simple to simply select a line, right click, select similar and use a palette to set the width of all associated, similar plines?