The garment industry has created disposable fashion because that way, it can sell more clothes. It wants rapidly changing fads and it wants people to feel forced to constantly update their wardrobes to keep pace. Because this makes money. And at very high profit margins, thanks to the exploitation of garment workers who produce the cloth, the finished clothes, the accessories at very low wages and in grueling conditions. The industry forces women to be complicit by making timeless garments produced in ethical ways unaffordable. $100 or $14 for a scarf? You choose, ladies.
This is actually the topic of my thesis. Just FYI, tumblr-land.