Because we are conditioned from the time we are born to want more, more, more. More money, more stuff, more kids, more toys, more love, more, more, more of everything. People place too much emphasis on what they "should" have or want, rather than what they do have or need. Anyone can see we are bombarded with new products on a continual basis. Nothing is ever good enough...you've got to have the newest and greatest!
But the truth is, "stuff" never made anyone happier - not in the long run anyway. In my life of 51 years, I have had lots of money and then had none; Had money, then none and so it goes... I realized that it didn't define me. What made me feel "satisfied" was appreciating my life, myself and the people in it. I know that if I never had another penny in the bank, I have people who love me and care about me. I believe that satisfaction comes from within, not from without - and that's the problem with our society. We are too driven by "stuff".