The need i suppose exists in all of us, even the want.
I believe that the main factor that effects it out side of the science of the human brain is in our upbringing, woudl be the 'drive' that is instilled in us by our parents, or lack there of in some people. While i do realise that in some rare cases the drive might not be placed in by the parents, but still a person has it. A friend of mine's father was a dead beat and mother was a stripper, neither of them cared about anythign but their next line of blow. Yet my friend makes about 80 grand a year as a mechanic for a heavy equipment firm here so i suppose there are acceptions.

G-man