I do not think it has anything to do with morality, other than in a very superficial way i.e. as ex post facto justifications of one's preferences (but that what the nature of morality is anyway, no?). The varying desire for "eternal rest" "cushy" life or certitude are determined by person affective and cognitive disposition, which in turn are determined by the chemistry of our brain. Some people have affective disorders that make them depressed and pessimistic in situations that other people do not see any reasons for despair. But being pessimistic is not a moral choice but an outcome of our neurological process, as evidenced by the fact that these moods can be altered by chemical means (i.e. by changing the neurotransmitter seratonin reuptake process).
In the same vein, some people have low tolerance for change and ambiguity and feel frightened and threatened in situations that most people are not. Cultural expressions of such affective states can be a desire for "eternal rest," peace or certitude. A dose of mood stabilizer may be enough to cure them from their fears.
PS. I also believe that these things, which are the basis of our political and moral views, are hereditary, just like other affective disorders.
Wojtek