First of all, in the early nineteenth century, the Victorians standardised the tunes of all of the Christmas carols, and established a sort of Canon of acceptable carols. So you couldn't sing "While Shepherds Watched" to the tune of "Ilkley Moor" any more, because that wasn't the proper tune, while "The Joys of Mary" hadn't made it into the Canon and so survived, insofar as it has survived, as a folk song.
Then along came "Carols For Choirs" - when? in the late 60s? - and not only were all the standardised carols from the Canon reset, but the settings themselves became standardised, so that every choir in the land, every school carol concert, every group of four girls shivering in the High Street raising money for Christian Aid is going to sing exactly the same descant to the third verse of "Hark the Herald Angels", and however fresh and original it was 40 years ago, it is now a tired cliche.
So I think the Naxos Book of Carols (which I have just discovered but which is five years old already) available as a CD for a fiver, or as a book with SATB score and CD for less than a tenner is very welcome, just because it is new and refreshingly different, and, at this time of year, cheap!