Why, in your opinion, not?
My understanding is that IHT will apply to farmland in Ltd cos too. But even if I am wrong, for smaller family farms becoming a Ltd co adds a lot of costs and complications for businesses that are already making small profits. Another issue is that a farmhouse in a company would be subject to CGT. They often cannot be separated from the land in the eyes of the HMRC.
It is certainly not straightforward and I guess if it was, then there would be no reason for farmers to demonstrate or any point in the gov changing the rules in the first place!
Ps im not an accountant so please correct any of my statements that are wrong!