According to Tesco, it's all to do with image. "Sandwiches are usually eaten at your desk, and everyone looks to see what the next person has bought," said a spokesman.
Well-paid executives invariably insist on designer sandwiches, made from speciality breads, rather than a humble sliced loaf.
It appears businessmen don't want to be seen with a humble cheese sandwich. "They want to be seen as sophisticated and knowledgeable about food - and a sandwich which stands out in a crowd is used to give them psychological edge over their rivals," said the spokesman.