Have a look at the history of western settlements in the "new world" and you will find that it was not a healthy enterprise. Disease, injury, starvation etc killed off massive numbers before they either acclimatised or learned how to deal with the hostile environment.

I can't see space exploration being any different. The only difference is that current society is fairly comfortable so the idea of leaving your comfortable home to risk everything on travelling to a new settlement on an other planet is distasteful.

Give it a few years and the situation on Earth may change, climate change, over population or simply the political situation may make travelling elsewhere more attractive.