The idea with the towel wrapping is not to hide it but to protect it, at the same time making it look like it's used. Like you said, you can't hide anything from customs anywhere, and you most definately do not want to be on anyone's book.
I guess customs are more restrictive where you're located. It's not unusual for people here to fly to Miami, buy all they want, then come back in the afternoon, and pay nothing at customs.