Do you know why you work?

While at work last week, a couple of Co-Workers and I got on the conversation of why we work.
Do we work for ourselves, do we work for our family, or do we simply work because we are taught
to as a child and we are just following suit? Of course we work for the money, that's a given but
why do some of us work for less then what our work is worth? Had one co-worker tell me we work
for housing and food, well if this is the case, why not stay at home with your parents. I think we
work because that is what we think we are suppose to do and we want to keep up with the rest of
the world. Because it doesn't cost a dime to build a hut and food comes from the earth. So at the
end of the day "What do you work for"?