I think there are some people who can only find happiness in always striving for something. Sort of like an explorer - he does not explore to find a better place to live in, he explores because it's the exploration that is what makes him happy.
So for the people for whom the search is happiness, it will look from the outside like they are never satisfied, but they were satisfied already when they went from nothing to almost nothing.
I would agree that part of the enjoyment of life is continually striving, or growing. For me, that exploration is less physical and more intellectual/emotional. And maybe I'm biased, or hitting this point too hard, but I would again argue that those who search for a better place to live in physically (a bigger house, etc) will be less satisfied than one who strives for a better place emotionally/intellectually.
So for the people for whom the search is happiness, it will look from the outside like they are never satisfied, but they were satisfied already when they went from nothing to almost nothing.