Psychiatry adopted the biological model for mental illness due, in large part, to medical economics and also because psychiatrists want to be counted among “real doctors.” The biological model allows treatment of all psychiatric disorders with medicine and dramatically increases the number of billings per day. (Medical economics)
Like, for example the abnormal EEGs associated with some affective disorders, the ways some drugs can cause clinical depression or greatly exacerbate it, or the remarkable responses (reported, often, not by the patient but by the family, friends, and associates of the patient) to some medications?
Or, on a larger scale, Are all opinions determined not by evidence but by the desire for some kind of gain? And if so, is the opinion that opinions are so determined itself so determined? Certainly the opinion that opinions are determined by economic gain and power would fallunder the genral classification of "Marxism", and while there are many problems with Marxism, the first is the problem of how does Marxism explain Karl Marx?
And what is "Psychiatry" that "it" can adopt or reject models?
Having said all that, I will eagerly agree that medical insurance companies sure wish that all psychiatric problems would respond to medications which are often cheaper (and more effective, maybe) than "the talking cure".