The cc is only a guarantee...they aren't charging a deposit. They only charge the card if you don't show up or cancel within 48 hours, and I think it's $10 per person. I think it's basically due to the popularity of the restaurant, especially during fireworks times. This guarantees that more people will show up for reservations or cancel within reasonable time so that the restaurant doesn't end up with a bunch of empty tables when people get "stuck" in the parks and decide to just skip the dinner. It also allows people who were "shut out" to have a crack at last minute cancellations as late as 2 days out.