Maybe it was the fact that, back in the day, gundogs were owned by those who were dead set against poaching and very few ever were used for lurcher production and so stayed out of vogue for years after.
Then Plummer in his early books stated that there would be lots of 'waistage' in litters, putting off potential breeders and strangely enough this happened just as his mate was starting up a commertial collie cross venture....
As has been said, the ones i've seen have been top notch and yes AT, why ain't you ever got one, I recon they'd suit you down to the ground..?