They were all distinct individuals with most of them there to make a buck. Not much idealism in most of them.
And it makes sense that Weyland chose such people for a mission that he hoped would save his life? For someone who had accomplished as much as he had, those were some remarkably bad decisions.
Unless Vickers picked the crew, in which case it was equally stupid for Weyland to give her that responsibility. No matter how you look at it, it's just flat out dumb to hire people who only care about money for a mission with such high stakes.