It seems highly highly highly unlikely that (in whatever state you practice) disability evaluations are something physicians are legally obligated to provide.
Edit: After reviewing SSA.gov regulations, it looks like you can refuse to do the evaluation (potentially with good reason as the treating physician is not quite objective in disability assessment) and the SSA will pay for an independent examination.
I work in a setting where I get asked to write disability letters and emotional support letters in at least 1/3 of my pts, roughly.
I never do a disability letter. I document my findings in my notes. They hire their own independent doctors anyways, as you said, personal physicians are often biased/coerced by patients so they have someone else look at all the records.
In my experience, most disability requests that I personally receive are BS. Could be my setting. Had a woman yesterday who is trying to get disability because "her foot swells". I asked her why she couldnt apply for a job that allows you to sit down and she just simply said "well then i couldnt get disability".
I understand disability in schizophrenia/psychotic disorders or bipolar 1, but in most other psych disorders, seems ridiculous usually. Taking people out of the workforce and getting rid of drive/goals is counterintuitive to treating depression.
There was a provider here who would write letters for anything, a while ago. He wrote a letter for emotional support dog, then the dog attacked the neighbor to the point of the neighbor having to have surgery.
Usually when people want an emotional support animal, its as others have said, so their dog can live with them in their apartment or something of the sorts.
I don't mind FMLA and school accomodations but my goal is to keep people working/independent. I have people with schizophrenia that are working, and have improved because they work. Physical activity is great for mental health, after all.