Why would I disagree? Well....I fill on average 180 prescriptions per day - lots of those for a variety of antidepressants, mood altering, antianxiety, etc medications from any number of different medical specialties - FM & OB/GYN included. I also worked for 20 years in a hospital with an acute inpatient psych unit in which my responsibility was chart review & patient drug education. My PERSONAL relationship with these prescribers, especially in recent years, has been that patients get referred to the primary provider when the patient becomes stable or has circumstances which prevent the patient from utilizing a specified mental health provider. In addition, many of these medications are used by oncologists, pain management physicians & neurologists for treatment of depression (sorry - don't really know the diagnostic terminology) associated with an illness which they are managing. Physicians communicate with each other all the time - you may just not be aware of it.
The reality is some insurances do not provide for mental health benefits and most, if they do, place limits on how many times or how much money is spent on utilizing these services. For these patients, it is in their interest to have their continuing medical needs followed by their primary provider, who can consult with the psychiatrist, if access or plan limitations prevent continuing treatment. It is better they are followed by a physician rather than not being able to access anyone at all.
I will agree with your assessments with regard to dentists & mental health issues since you are a dentist & brought it up. I can only agree though based on my own limited experience with my husband and his colleagues, who are personal friends. Uniformly, they do not know these drugs side effects (but, my husband does not know what felodipine is used for either!), but they call the physician if it will impact treatment. Few root canals need to be deferred because the patient is tapering Effexor or starting on Wellbutrin, but you may have a different practice than that of my husband.
I'm not clear why you might want to limit prescribing authority. Take your area of expertise...you prescribe chlorhexidine as a mouth rinse - that is its only approved indication. However, dermatologists use it for some of the conditions they treat. Prescribers - all of them - take on the responsibilities of what they do seriously. I have never, on rounds, during my hours of chart review & in all the various ways I've had to contact them have ever not taken what they do seriously & in a considered manner. Sometimes, bad side effects happen and it takes more adjustments than some might want to find a stable therapeutic plan, and sometimes patients just dont click with providers...but that is not a reason, IMO to chastise the whole bunch of non-psychiatrists. That said....your personal experience may be far greater than mine.....