I think this vastly oversimplifies the problems associated with getting an appointment to see a doctor. I am a child psychiatrist. There is an estimated need for about 12,000 child psychiatrist by 2020, but there will only be about 8,000 practioners. I see the effects in my own practice on a daily basis, where the wait to see me is about 3 months, and I struggle to have a follow up of even an abbreviated time in 2 months. Same day scheduling would not be practical, as I need information from schools and therapists.
In addition, I find the restaurant example to fall apart (or at perhaps to support my views?). Locally, most restaurants do not take reservations. When I show up at dinner time, there is often a wait of several hours, which discourages people from staying. Perhaps in urban settings with a greater variety of choices in both restaurants and physicians, this analogy holds better, and maybe medical access could be simplified. But for now, the restaurants don't do any better at getting me access to food than I do at providing access to treatment. In both cases, I think the solution is to have more providers, a task not easily accomplished when the training period for child psychiatry at least is 13 years of post-high school education.