Why is the Hadd not applied to a deliberate murderer if the murderer is one of the ascendants?

A parent is not to be executed for (killing) their child for several reasons: the existence of the explicit prophetic text, "A father is not to be killed for (killing) his son"; that the parents are the cause of the child's existence, so the child should not be a cause for their demise; that Hudud (punishments) are averted by doubts; and the Hadith "You and your wealth belong to your father" is considered a doubt that averts the Hudud punishment.