Why are people are often reluctant to (organizational) change?

As I read this question I just had to think of Prospect Theory: People tend to preserve what has been proven successful until now because that stands for stability and security (a sure win). The new unknown stands for risk (a potential loss). Like in Prospect Theory its about securing Sure wins (vs loss aversion). Perhaps the Prospect Theory can also set impulses in change management (just a not thought-through quick idea)