why do we follow harmful traditions
One explanation for following harmful traditions is the heard instinct, or the use of a rationalization process to justify choices that are being followed by everyone else. Economics is an example. If I have a house in a certain area, and suddenly everyone starts selling their houses on that area, I will think that I should also sell mine before the price goes even more down, which will make the prices in a total go down anyways. This happens because people look to others in clues in how to behave. When going to the gym, we will look around to see how people are dressing and try to dress adequately to fit in the situation. When going to a wedding, we will dress appropriate to look like everyone else.
Another example can be kids, which claim they need a cellphone, since everyone in school has a cellphone. This can bring cultural lag, since some harmful practices are from thousands of years ago, such as in some religions, such as Judaism, sacrificing animals and not lightning any candles in Shabbat are still practiced today, which is different in a time where it is hard to do anything on Saturdays, because some people live in apartments with elevators, or where there are automatic lights, and times changed from the time where the only “light” we had was candle light, and therefore this practice is still in place today, where the conditions are very different than thousands of years ago. The same explanation can go to harmful traditions, such as the baby dropping ritual, in India, which is done for over 500 years, and believed to make the baby grow healthier. Such acts are either justified by appeal to traditions and the heard instinct of following everyone else.