Here's why:
* Ritual Monsters are Summoned with Ritual Spells: Ritual Monsters are summoned using a specific Ritual Spell card that corresponds to the monster. These spells require specific tribute monsters from your hand or field.
* Ritual Monsters Cannot Be Summoned Directly: You cannot directly summon a Ritual Monster from your hand. You must use its corresponding Ritual Spell card and meet its summoning conditions.
* Tribute Monsters Must Be on the Field: The tribute monsters required for a Ritual Summon must be on your field, not in your hand.
Therefore, you cannot tribute a Ritual Monster from your hand to summon another monster.
Let me know if you have any other questions!