Here's why:
* Summoning Conditions: Ritual Monsters require a Ritual Spell and specific Tribute Monsters to be summoned. This process takes time and resources, usually preventing them from being summoned on the first turn.
* Ritual Spell Activation: Ritual Spells must be activated during the Main Phase, and they need to be resolved before you can summon the Ritual Monster. This takes at least one turn.
Exceptions:
While generally true, there are some exceptions:
* Fast Effect Ritual Spells: Some Ritual Spells have a fast effect, allowing you to activate them during your opponent's turn. If the spell's effect allows you to summon the Ritual Monster immediately, it might be possible to attack with it on the first turn.
* Specific Monster Effects: Certain Ritual Monsters have unique effects that allow them to attack on the first turn. However, these are usually specific to those individual monsters and not a general rule for all Ritual Monsters.
Overall, it is extremely rare for a Ritual Monster to be able to attack on the first turn. The typical process of summoning a Ritual Monster usually requires a full turn to complete.