You haven't posted in such a long while that I missed this.

To paraphrase Nietzsche's 'men will rather will nothingness than not will', I'll say that 'men will rather invent causes than leave things to chance'.

There's so much psychologically involved in this. For instance, if you got the disease cos you were morally at fault, then there's hope that you can change your situation by righting the fault/wrong, by making amends, by asking forgiveness, etc.

So I think it's partly people stubborn meliorism - their belief that there's always something they can do to change their situation into something that agrees with their desires - that makes them unsatisfied with 'chance' being given as a reason.

At any rate, it serves us very well, evolutionarily, to always look for causes, even when there's none to be found.