I don't think many people ever really grow up.
Sure, physically we reach maturity. Most people even reach a certain intellectual adulthood. But most folks never get out of emotional and social adolescence.
In a democractic republic with universal adult suffrage, that is a recipe for disaster. As the people lose the ability to balance their checkbooks and make prudent fiscal decisions and generally behave as responsible adults, so goes the country.
My generation may well be the first generation of Americans ever (certainly since the Great Depression) to leave its successors a nation that is in worse condition than the one our predecessors left to us. Public debt has ballooned, in large part due to our inane tendency to try solving every problem by spending money on it. Our military is the functional world police force. The economy is increasingly reliant upon externalities, leaving us vulnerable to forces beyond our control.
Spending more money cannot save us. Saving more money cannot save us. Making more money cannot save us. Using what we have prudently and efficiently and learning to be content with what we have may be our only hope. But that is increasingly unlikely in a world where people believe access to the internet to be an inalienable and basic human right. How reassuring to know that my ability to blog is apparently as important to life as my access to proper nutrition.
Children want to have it all. In that regard, I don't see much difference between a child and the average American adult.