I should think many superstitions began as sensible reactions to cause-and-effect. No new shoes on the table, for instance. Could it be that if the new shoes were made of leather from the hide of an animal which had died of anthrax, enough of the spores of the deadly disease remained to contaminate the table or any food on it and cause a death in the house? Before the means of the spread of infection were known, it was just a mysterious and unpleasant death. It is an unlikely thing to happen now, but the superstition would be remembered.
Maybe if people who are plagued by superstitious dreads could analyse why certain things or actions became a cause for worrying they would be able to ignore them?
Religious taboos (some seeming very similar to superstition) might date back to genuine safety concerns, too. Take not eating pork, an ancient dietary rule which is also followed by people with no religious reason to do so. In Old Testament times, most people in the Middle East lived their lives in small villages with little or no sanitation, using the great outdoors instead. There was no municipal cleaning department either - that function was performed by wandering swine, who ate anything they could find lying around. In these conditions, pork could easily become infected with parasites, picked up from the faeces of an infected person. I won't go into the life cycle of that parasite, but if you didn't eat pork, you avoided infection. Nowadays pig farmers are careful what they feed to their pigs, but the habit of not eating pork lives on.
