Out in ya'lls area you have a number of teams that use offset type stickburners and they can flow a lot of air.
Thus, they may feel the need to use a "mop" while cooking.
Like the cooks above say,the FEC doesn't require it.
When you get south of there ,with the TX bunch,you can be disqualified if they catch you saucing,after cooking.
Now,down South,many of our contests can look like sauce contests for the chicken and rib categories.
Doesn't mean it is a great idea-but.
Seems like many of us like to use just rub,to make a fine backyard slab of ribs-when we are home.