Why we change our old things for new things?

In our society the idea of save old things (of course they need to be in a good condition, they don't hace to be broken) it's not common because every day we are manipulated for a society full of prejudices. Why we have to quench our wish to have the best and the newest? Simply because we  are happy, living with that philosophy. We should change our vision about what we have because when we see a video about the third world we'll be more thankful. It's not about money it's about our mentality because some rich people tries to make this world better trying to contribute on benefical causes.