One of the biggest factors for success in life is the ability to cope with delayed gratification and to show restraint. Yes, opportunity cost is huge for kids,

One of the biggest factors for success in life is the ability to cope with delayed gratification and to show restraint. Yes, opportunity cost is huge for kids, and they might rationally spend all money immediately. But that's still not what we encourage... So we'll put our finger on the scale and adjust situations to make saving beneficial.