Here's why:
* Synchro Summoning Requirements: Synchro Summoning requires you to have specific monsters on your field (face-up in your Monster Zones) that meet the summoning requirements of the Synchro Monster you wish to summon.
* The "From the Field" Rule: Synchro Summoning specifically states that the materials must be "on the field" in order to perform the summon. This means they cannot be in your hand, deck, or graveyard.
However, there are some cards that can help you Synchro Summon from your hand in specific situations:
* "Quick-Play" Spells: Some "Quick-Play" spells, such as "Synchro Summon" can allow you to Synchro Summon from your hand. These spells usually have specific restrictions, such as requiring you to have a specific Synchro Monster in your hand.
* "Effect Monsters": Some "Effect Monsters" have effects that allow you to Synchro Summon from your hand. For example, "Junk Synchron" can be sent from your hand to the graveyard to allow you to Synchro Summon.
Important Note: These are just some examples, and there are many other cards with specific effects that can modify Synchro Summoning rules.
Always check the card text carefully to understand its specific effects and restrictions.