What is even more crazy about this whole thing is that instructors will take students off a LARS frequency onto 121.50 to do the practice pan! Why not simply tell the LARS or Approach or Tower or the FIR or whoever one is in contact with that one is lost.
To give the student confidence that they will be heard (almost) anywhere in the country, that auto-triangulation works and that D&D will not bite his or her head off (they don't - they are quite happy to do the 6 or so a day and encourage the practice).
I don't however see the need to do a practice once someone has a PPL or better.