nice to see your post.
i have had mental health problems all of my life. the first time i got professional help was when i was a teenager, in the 1960s. that pdoc did both prescribing and therapy. since then, except when i was an in-patient for a month in 1972, the pdocs have done the prescribing and a therapist did the talk therapy. i agee that this situation is not ideal. my new pdoc in al does both a med check and therapy during an apt. shocked me when he told me.
my cynacism says that at least part of the reason for this separation is money. by the time a student is able to hang out their shingle as a pdoc, he/she is, on average, in debt over $50,000. insurance companies (including medicare) only pay the doctor pennies on the $ for their work. however, a pdoc can fit in a lot more patients doing med checks (as you say, 10 mins for a 20 min session) than in doing therapy (perhaps 1 patient an hour). in either case, they are reimbursed only 50 % of their normal fee by the insurance companies for either med check or therapy.
i don't know if what i'm saying is the sufficient cause or contributing cause or no cause at all. its simply an observation. old men are allowed to observe (but not touch - lol).