The difficulty seems mainly to arise because up until now no-one has thought through how to best use the skills of both pilots if they are flying in a "single-pilot" aircraft. I understand the PPLIR Network has a working group studying this subject at present. After all, it is fairly common to have two pilots in a "single-pilot" light aircraft. I always find that sharing the workload when flying with another pilot makes sense PROVIDING we have agreed in advance who does what.