It used to be thought that appreciating the advantages of an action would lead to a change in behaviour. In a rational world, once you’d understood the benefits, your behaviour would logically adapt. Not so. In real life, we act on seemingly irrational and inconsistent impulses. We are affected by things in our environment that we may not even be aware of.
This supports commonsense, and the often-experienced reality that nagging a young person to change doesn’t work. Incentives, however, may well be much more effective. A deal such as, “If you set up a savings account and transfer a regular amount to it, I’ll give you a pound every Friday” is simple. It might work better than any amount of arguments and logical persuasion.