Why?
I could understand the point of them if they were small workers cottages, in a similar way some houses are subject to only local residents buying conditions, this reduces the price in a similar way an AOC does. AOC is always massive great houses though (well, I've never seen otherwise) very often without any land, so it's not the farm they're buying. If you can afford to spend one million plus on a house, why should you get to buy it cheap? Just seen one including six holiday cottages wtf!
For information, if you don't know, this is what I'm talking about.
“The occupation of the dwelling shall be limited to a person solely or mainly employed in the locality in agriculture as defined in section 336 of the Town & Country Planning Act 1990, or forestry or a dependant of such a person residing with him or her or a widow or widower of such a person”.