I realize that this highly depends on the country and its medical system.
I live in a country where there is universal healthcare and you can just book an appointment with any doctor of any kind without going through any gatekeeping.
I think the placebo effect is at work here: While I don't doubt any nurse could handle 95% of the cases a general practitioner has to face here every day, elderly patients want that expert opinion from the guy they value highly and trust in so much.