In Dogs and All about Them, written by Robert Leighton in 1934, we find the following passage about the demise of smooth Fox Terriers as working dogs:
Whether the present Fox-terrier is as good, both on the score of utility and appearance, as his predecessors is a question which has
many times been asked, and as many times decided in the negative as well as in the affirmative. It would be idle to pretend that a great many of the dogs now seen on the show bench are fitted to do the work Nature intended them for, as irrespective of their make and shape they are so oversized as to preclude the possibility of going to ground in any average sized earth.
This question of size is one that must sooner or later be tackled in some practical way by the Fox-terrier Club, unless we are to see
a race of giants in the next few generations. Their own standard gives 20 lb.--a very liberal maximum; but there are dogs several pounds heavier constantly winning prizes at shows, and consequently being bred from, with the result which we see. There are many little dogs, and good ones, to be seen, but as long as the judges favour the big ones these hold no chance, and as it is far easier to produce a good big one than a good little one, breeders are encouraged to use sires who would not be looked at if a hard-and-fast line were drawn over which no dogs should win a prize. There are hundreds of Fox-terriers about quite as capable of doing their work as their ancestors ever were, and there is hardly a large kennel which has not from time to time furnished our leading packs with one or more dogs, and with gratifying results. It is, therefore, a great pity that our leading exhibitors should often be the greatest delinquents in showing dogs which they know in their hearts should be kept at home or drafted altogether, and it is deplorable that some of our oldest judges should by their awards encourage them.