If you didn't have the
DDP then you would be billed immediately for CRT (two of our party is going there for date night, and I paid for it as a birthday/Christmas present for them and it's already shown up on my CC statement), it's such a hard-to-get reservation/it's a fixed price meal that they have you pay in advance.
Everything else though, like Capang said, is just as a form of insurance. If you cancel a reservation less than 24 hours in advance or you don't show up and don't inform the restaurant they will charge you a fee ($10 per person on the reservation).