If you have had any biopsies done, and if they don't reveal any forms of microbial infection/infestation then, this may be the reason why the leave it alone method seems to be working for you. However, I have noticed that a plateau is reached rather quickly with the leave it alone method & thus the sufferer almost always goes the moisturizing route.
Keeping contaminants in the air out while a wound is trying to heal is the main function/priority of a scab. I believe that the buildup is acting as a scab to try to assist with healing. However, where it helps with keeping out aerial contaminants it also serves as a breeding ground for other bacteria being how it is located on the mouth.