I do not know the background, but we have observed this phenomenon. It's connected to what is happening in the United States. Nutritionists have opted for a daily recommended intake, because it is important to have a figure associated with every nutrient, among other things, because children do not eat as much as adults. They opted for this approach a long time ago and it will be hard to change it.
On November 16th, 2009. See this statement in context.