I think of lucid dreaming as an art. To that end it can never be mastered because the possibilities are endless. I'm pretty much as proficient as a natural lucid dreamer gets (I can get around 1-3 LDs per night with detailed and authentic experiences) and still I make no attempt to claim that I am a "master."

WILD requires mental discipline and rigour. No human alive has that level of mental control, therefore they can not pull off "perfect WILDs."