I think it can be pretty complex. A lot of people (especially older people) will have a preconceived idea of what they have, and come to the doctor only to get confirmation, or have a prescription. Then some will only take the drugs matching what they think they have, and just ignore everything else the doctor told them (my parents do that).
Or for people with chronic issues, there isn't much mystery about what's going on, only some variations between a month and another, most of the time. What's special is that the patient will be motivated enough to do a lot of research (in the time there was no internet, go through medical documentation, even research papers), taking time to understand well enough what's happening to them. Then, a doctor might diagnose something different than their previous doctor. Or prescribe different drugs with different side effects. Or sometimes the doctor might not be as well informed on the subject as their patient is, because it's not their specialty for instance.
These might be the cases where having transparency and trust between the doctor and patient are the most important and crucial to have the patient cooperate.
Or for people with chronic issues, there isn't much mystery about what's going on, only some variations between a month and another, most of the time. What's special is that the patient will be motivated enough to do a lot of research (in the time there was no internet, go through medical documentation, even research papers), taking time to understand well enough what's happening to them. Then, a doctor might diagnose something different than their previous doctor. Or prescribe different drugs with different side effects. Or sometimes the doctor might not be as well informed on the subject as their patient is, because it's not their specialty for instance.
These might be the cases where having transparency and trust between the doctor and patient are the most important and crucial to have the patient cooperate.