Someone who accepts the 'risk' of certain death on the mission doesn't seem to me to be the sort of person you want as your companion on a dangerous voyage. And if you're planning to found a colony, you want all sorts; not just nerds, scientists and technicians.
That is EXACTLY the person I want around, because I know they can be relied on even in dangerous situations. You, on the other hand, who thinks that someone who does not fear death would be a bad companion on such a mission, would likely piss himself in face of actual danger.
Someone who's afraid of death on a suicide mission is a danger to the mission and, thus, to myself. When you want to found a colony, you need strong men and smart men, best when each man covers both.
You definitely just want nerds, scientists, doctors and technicians, because they get the shit done.
This isn't a hollywood movie.
Why do you think such people are reliable?
For clarity, I'm not afraid to die. For exactly that reason, I think I'd be an unreliable companion on a dangerous mission. For my companion, I'd want someone who thought they had at at least as much to lose as me. If you want to head off to Mars with Rambo at the controls, that's up to you.
If you want to found a colony that is all scientists and technicians, because you don't think ordinary people "get things done", good luck with your colony. Pumping sewage, helping people in mental distress? Sure, leave it all to technicians; after all, we'll filter them for mentail susceptibility before they leave. We're good at finding nutters before they go nuts, aren't we? Well, no.