1. Emergency frequencies are there for one reason: To use in an emergency !!!
2. Every pilot / controller should monitor this frequency whenever possible, it can save your life or someone else life!
Practice pan calls can be done in other ways f.i. On a normal Atc frequency when the frequency is not too busy.
The only place in the world where they do these practices are in England, the rest of the world is not doing it!
This has nothing to do with forgetting how I was trained when I learned to be a pilot, I was never trained to do practice pan calls on an emergency frequency.