Yesterday I made a reservation for clients at my favorite restaurant. The owner (who I know well) asked me to PLEASE make sure that the clients call to cancel if they decide not to come. She said that now, more than previously, Americans are making reservations at restaurants in Provence, but then not calling to cancel and not showing up.
Just the day before a colleague told me that she had made reservations for 8 at three different restaurants in the St Remy area. The people never showed at any of the restaurants. All three restaurants called to tell her about the no-shows, and also said that they had held the tables (some for 2 hours) as a favor to her. Restaurants here are not large so one table of 8 that doesn't show can make a difference, especially in summer when places make most of their money.
Please ask your friends and family who are coming to France to cancel reservations when they change their minds about going.