Why is it important to Juana that Kino be the one to throw the pearl back into the sea

Their lifestyle is one in which Kino is the man in the family and should be the one to take the lead in all things that relate to the development and protection of the family. Further, Kino took the pearl from the sea, so it is his responsibility to return it to the sea.

They are the ones who found it. THe power of the pearl affected their family so they must be the ones to rid themselves of this bad energy.