One distinct reason why there could be no unity amongst the doctors in Vale View/ Aberalaw is because the community held all of the power. The patients were able to choose their doctors, and in doing so, doctors had to appease them:
As he went round the town, calling on his patients, Andrew received many black looks. And there was worse trouble for him. The men had the right to choose their doctor. Each man gave his medical card to the doctor of his choice; if he wished to make a change, he could ask for his card back and hand it to another doctor
The "right the choose their doctor" plays a large role in the lack of unity amongst the doctors. Doctors were competing for patient approval, recognizing its importance. Any attempts at unity could undermine their own standing in the community, reflective of how doctors in Aberalaw/ Vale View were at the whim of public approval.
Andrew recognizes this in a direct way. His first morning's practice involves signing 40 leave notes for workers who want to get out of work. When Andrew stands up to one of them, Chenkin, and refuses to give him a leave letter, Andrew is reminded of the power that patients have in Vale View: “As soon as he had gone, Gadge entered, rubbing his hands with delight. 'Do you know who he is? His son is an important member of the committee.” Doctors like Andrew cannot forge unity amongst one another because of their insistent fear of public rebuke. When Andrew stands up to Chenkin and his nurse, it becomes clear that Andrew has established "enemies" and that there was an active campaign for all of the other patients to leave him. This reality in Vale View/ Aberalaw is one reason why there could be no unity amongst the doctors.