Why?

I am watching "Eat, Pray, Love" right now and really I think the Italians have it right, I mean I read the book a few years ago and loved it and my wanderlust was ignited and I did travel, to Mexico, to Ireland, to London and that wanderlust has cooled in the past few years as I have settled into coupledom. This type of settling is not like settling in a bad way but it has tamed the wanderlust because I wanted to make a home for us. And we are now getting married and I am very happy but still I wonder as Americans, why do we do what we do? We work 40-60 hours a week and the time that we have off is spent in a coma trying to recover from what we just did. But, why the hell are we still doing this to ourselves? What are we try to get to? The million dollar mark or the giant house and the BMW? But then what, once we have gotten the things we wanted, where do we go from there? I am guilty of it as then next person, I work at a job that I like but it doesn't fulfill me and I am in grad school and am so totally bored by what I am doing. So why do it? Because of money I suppose, because I want to have a family and allow my children to travel and live in a way that allows them some freedom to choose what they want to do based on what makes them happy.
We need to be told that we have earned things, a vacation, a Gucci bag (or in my case a LV bag that I have been lusting after for years) but why, our basic instinct tell us that we want something and to go out and get it? Why must we put such restrictions on it?