So, what is the motive behind this parental behavior? Why do parents lie to their children? It seems that parents lie to their children in order to shape their emotions and behavior. Parents sometimes lie to their children to get the desired behavior, such as lying so that the child will not cry during a night out dinner, or even for protection, such as lying so that the child will not learn about the horrendous murder in the news.
But is this really beneficial? Granted, I am not a developmental psychologist, so this is just my opinion out here. But I would think that lying actually disrupts the learning mechanisms of the kid. If the parent lies by saying that a magical creature will be happy if the child ate his broccoli, then the child will form the wrong assumption of a non-existent cause and effect. I think it would be way better to expose children to truths in the very beginning.
I do understand that there are cases in which experience trumps learning. There may be times in which it is way practical to tell the child to just obey, since the parents know better. But children are not stupid. Children have fascinating brains too, and they have the amazing capability to learn quick. Parents may just be under-estimating the capacity of the child's brain for learning, to the point that they will lie more often than needed. Children can recognize patterns and rules, and they are not stupid as parents might think.