Reading about the short documentary of three volunteers for Mars One (http://mashable.com/2015/02/09/mars-one-documentary/) made me think about their cores, their Why's to why they would want to die on Mars.
First, the push: disappointment in Earth, and perhaps even humanity. Natural disasters, inequity, and diseases are just few of the reasons why they are leaving.
Second, the pull: the search for happiness. The promise of adventure, hope and greatness, the belief in what they are risking their lives for.
Common people will call them crazy. But to jump on such thoughts is just a sign of ignorance (link to post 2 Apr).