Proably since agricultural marigns became tighter, in the past certain losses may be tolerated but when things are tight u can no longer tolerate the same losses.
Is it any difference to ur neighbour and his pigs? If u have a crop that pays ur wage then if any animal starts turning it from be profitable or vaible then it will be a pest and treated so.
I know of 2 big local estates that until 15 years ago u were not alowed (meant) to control foxes on and both had big shoots with 2-3 FT keepers, when an animal is pest/vermin on 1 side of the fence but sport on the other, is just a opinion/viewpoint
In the vast % of uk farms deer aren't seen as a big problem, infact most farmers like to see them (mainy roe, althou a lot of farmers hate the fallow locally but numbers are very very high) roe do very little real damage to farm crops, even to timber crops after first 5 or so vurnable years.
Like everything else it all depends on ur view point and wot ur crop/job is 1 mans sport will always be another mans vermin
Shooting/stalking/keepering is a funny old thing that many folk are happy to do for free if not pay for the privaledge yet there's also folk who will go on and actually charge for doing wot many would do for free.