Lets be honest, individuals have an enormous impact on history and it is essentially random who gets born, who dies of disease, who gets injured and so on. Alexander the Great could have died of typhoid at the age of two, he could have fallen down some stairs or he could have been hit by a rock on some battlefield. The same could be said for any other figure in history. Although Lincoln might have been in less danger from rocks.
Part of it is that a given historian wants to display their research and their book needs a conclusion. I suspect, however, that the deeper reason is the tendency of humans to prefer discrete cause and effect. The historians ignore chance because it's uncomfortable and they don't know how to deal with it.
I guess I would at least prefer an acknowledgment of the role of "luck" in how things turn out. There are billions of people in the world so I imagine that events with billion to one odds are occurring with great regularity.