The server asks if you're on DDP, I'm not sure why anyone would consider lying
The server wants to tell you what's included, what's not included and doesn't want to have to ring up the check twice. Most restaurants let you switch from a soft drink to coffee with dessert. A few restaurants will charge for coffee. Next year the server will probably also explain that the gratuity isn't included.
Reservations asks so they can tell you if a restaurant is participating, if the restaurant requires two credits and in the case of dinner shows check the appropriate tier of tables. Initially the restaurants wanted to know because DDP tend to order more appetizers and restaurants were running out.
According to some servers the number of tables using DDP is frequently over 80% of the total. Some people are reading too many sinister motives into a simple question.
edited to say you're not calling your local restaurant, you're calling a central number that takes reservations for dozens of restaurants. That's not the same thing as calling ONE restaurant, where there isn't any question of a coupon applying.

Reservations asks so they can tell you if a restaurant is participating, if the restaurant requires two credits and in the case of dinner shows check the appropriate tier of tables. Initially the restaurants wanted to know because DDP tend to order more appetizers and restaurants were running out.
According to some servers the number of tables using DDP is frequently over 80% of the total. Some people are reading too many sinister motives into a simple question.
edited to say you're not calling your local restaurant, you're calling a central number that takes reservations for dozens of restaurants. That's not the same thing as calling ONE restaurant, where there isn't any question of a coupon applying.