I believe it's rooted in an uneasy relationship with God-as-Father, reflecting a pervasive dishonesty in the association with their own parents. I base this conclusion on my children's use of "just," either in petitions, "Could I just check my messages on the computer for a few minutes?" or in excuses, "I was just trying to see if Tom could really breathe underwater." Take it or leave it :-).
Please add me to your verbal mayhem ping list.