Tricky topic and no doubt you have already done a brain stormed list of possibilities and/or a Buzan Mind Map or Meta Planning exercise. I would think one big factor would be the complexity of dealing with the vast range of issues confronting the modern farmer.
There are technology and engineering issue of equipment and plant, Science issues of agronomy, Medical/vetinary issues of stock, Finance issues of funding, Business issues of planning, scheduling, storage, transport and costing. Labour issues and Legal issues. All these issues are constantly running through the heads of farmers many of whom recognise their inadequecy in one or other of these specialist subjects.
On top of this you have a political elite dedicated to controlling every aspects of rural life through rules, regulations and monitoring and, to top it off you have an urban intellectual elite who delight in proclaiming their moral superiority in matters of Food the Countryside, Animal Welfare and Countryside pursuits such as Hunting, Fishing, Shooting. Racing and even Agricultural Show standards.
How is the very small business to cope with all this? If the average farmer could articulate his feelings and what was happening to him in the same way as can the Man or Woman or Ethnic minority person before an industrial tribunal; the tribunals of this land would be awash with Farmers claiming Harrassment, or Discrimination by Defra, Animal Health, Trading Standards, Local Authorities, RPA. BWMB and all those other bodies that can make life intolerable.
Any small businessman/woman has more problems to deal with in a year than any bureacrat in a lifetime, but, by its nature, farming involves a degree of loneliness and solo decision making most other jobs do not require.
I'll quit now because I could go on and on and the TV company will not pay for ideas. What they should do however is spend time with a number of people from this forum and, like Prince Charles, learn for themselves what the technical, financial and emotional issues really are.
I know every group of people can make out a case to show that they are unique in some way or another, and this is certainly true of farmers and country folk. We are blest in many ways compared with our Townie cousins but the urban elite certainly know how to screw things up in the countryside.