Generally I think superstitions are useless and completely illogical & they make no sense at all!!!! Th only use we have for them is fun!!! we mention them and laugh at them that's the only useful thing about superstitions.
About the one u mentioned, I think aside than the fact that it is impossibly dumb!!!! It's also unhealthy for the kid!
im not superstitious person, but there are so many superstitious people in our country. for example some people believe that if you pour water on the ground behind somebody, when he or she is going on a journey, it'll bring him or her safely
I think some of the superstition -based stuff that people do have become rather symbolic ! they just pour the water to wish them luck ,not that they really believe in that.
turkish people say when there is a fitielye chai standing vertically in tea you must await a guest ! thus whenever such thing happens we get so excited that we actually invite some people to prove that it's true