If we pay OOP, we usually go for the cheapest items that appeal to us. With the
DDP, we feel that we can explore the more expensive items, things we normally wouldn't order, because of the cost factor. Of course, we will order something that we want to eat, but now we have a wider range to choose from. If a seafood dish is the most expensive item on the menu, but my DD hates seafood, she won't order it, just to take advantage of the DDP credit value. She may order the pork chop, instead. If we were not on the DDP, she would most likely order chicken, which is probably the cheapest menu item.
Along the same line, this is also true for the dining establishment. Because we are on the DDP, we can go to the more pricey restaurants, something we just won't do if we had to pay OOP.