I don't think requiring a formal appointment is a HIPAA thing; I think it's a money thing. Physicians don't get paid for phone calls (usually, unless they have some special deal with you). But if they get you in for a 15 minute visit, they get paid. If your blood pressure and pulse get taken, and a couple questions and such, they get paid MORE! (It counts as a more complex visit if they check different systems or something.) And as most of us would probably say, why work for free (phone call) when you can get paid for your work?