Comment by AussieWog93

The banks might pay 3% interest, whereas even non-volatile conservative investments like cap notes or bonds would pay something like 7%.

Plugging it into a calculator:

1.03 ^ 18 = 1.70

1.07 ^ 18 = 3.37

Example numbers, but you're effectively taking half of the money that your kid would have had on their 18th birthday, and giving it to a banker.