For the same reason it was effective for marketing: It wasn't immediately obvious _to anyone_ that the additives were ineffective. Very very often human beings

For the same reason it was effective for marketing: It wasn't immediately obvious _to anyone_ that the additives were ineffective. Very very often human beings have to make decisions based on incomplete data. If it had turned out that antibiotics in soap saved lives what would we be saying if the industry that had waited years for iron clad proof before taking the relatively inexpensive step of putting it in?