I think a lot people at times don't show up. Sometimes they cancel but it doesn't get into the system. We have gone by Guest relations & changed a couple of them & they never cancel the ones we were canceling but that their fault not mine But I think this can happen
I'm sure that 'no shows' is the reason that ADRs work the way they do. When you check in at your restaurant, they put you on the list for the next available table for your party size. An ADR does not mean that a table will be held for you.