It turns out, the ability to self-regulate (self-control), make decisions and take initiative all stem from the same, exhaustible, mental resource and takes a lot of physical energy to do. Like any mental resource, however, this one gets stronger with use. Thus, it is better to provide rules and structure for the young and old alike (even while knowing that the rules will be violated) because it helps the mind to become stronger at resisting impulses.
Willpower: Self-control, decision fatigue, and energy (RSA)
Roy F Baumeister - Willpower: Self-control, decision fatigue, and energy (TED)
As a side note, scientists recently discovered that consuming familiar, favorite materials (i.e. TV shows or movies that we have already seen or books that we have previously read, and that we enjoy consuming repeatedly) will "recharge" our willpower quicker than it will naturally recharge by itself. The benefit, however, does not come from consuming new material even if from in a favorite collection (i.e. a new episode of your favorite TV show). The original article can be found here.