We can take off with a 15 knot tailwing in A 320 series.
The reason for wanting to do 15 knot tailwinds is for one way runways or runways with substantial weight penalties due to obstructions. For landings, sometimes only one end of the runway has an approach and either circling isn't permitted by the approach or ops specs.
Good example for something like this is Lake Tahoe California, KTVL