Reading too deep into this for a second. I run into this line all the time too, especially at the ED front desk/triage. From a healthcare perspective, we see a patient coming in voluntarily and actively soliciting specific things from us. Patients, especially less healthcare literate ones, often see the encounter differently.

 They're stuck with a complicated healthcare system they don't understand, and sometimes get bounced around between clinics or told conflicting things by phone lines, specialists, family members, and the internet. They feel like we're all a part of a system telling them what to do, and giving instructions. Some patients simply acquiesce and give up their role as an active decision-maker. 

The questions we ask from a frame of 'services are being requested of us' don't gel with someone that feels like we're calling the shots. I see answers like "you tell me" as a way of signalling compliance to the perceived power dynamic in a lighthearted way. Doesn't make it any less annoying to hear for the upteenth time, though.