I noticed something similar when I compared my childhood with a kid of 14 years living next to my house. He too is equally happy and smiling like I used to be almost a decade ago, despite the fact that I didn't had anything like cell phones, Facebook, Twitter etc. The basic level of happiness of the average teenager has not increased in the past couple of decades years, even though we have all these new technologies and gadgets that make our life easier and more comfortable. And yet, every person would rather have these new devices than not have them.
I started wondering about this, since it has been my assumption that we strive to maximize our happiness, and so if an action has no long term effects on our happiness, why take that action? If I'd rather own these devices than not own them, it means that there is some metric other than happiness that is improved by owning them. I think that metric is 'CONTENTMENT'. I am simply more content owning these devices than not owning them.
And this concept applies not only to gadgets, but also to other aspects of life. Someone may work hard to get a promotion, build a big house, become rich, get a Nobel Prize, etc, even though after all these things are accomplished their 'basic happiness level' will likely not change.
What determines our happiness level is not very well understood, but after our basic survival needs are met, happiness is a function of things like brain chemistry predisposition, whether whoever you love loves you back, how well you get along with your significant other, how many close friends you have, etc.
Those things are unlikely to change just because you bought a new smartphone or a new Porsche or even because you won the Man Booker Prize. And yet, people strive for these things, not because they will be happier with the result, but because they will be more content with the result. They will be more content with themselves if they know that they have achieved what they wanted: bought a beautiful house, made partner in a firm, became CEO, won an Oscar.
People initially think that they are trying to maximize their happiness, but after a while, after achieving some early goals and not feeling happier, they realize that it's foolish to expect to become happier when the next goal is achieved. And yet, they persist on working towards that next goal. At that point, they are simply trying to maximize their contentment. It's just that 'the pursuit of contentment' is not as catchy as 'the pursuit of happiness'.
P.S.: I am no Great writer or Literature expert or English guru. This post is just a expression of my feelings and you might find some mistakes in it as it is straight from the heart and not proof read. Please ignore the mistakes. :) Thank you.