The issue with appointments is the provider needs to be integrated into the system. Apple can’t do that on their own. It would have to be more like the roll out of CarPlay. A couple partners at launch, a lot of nothing for several years, and eventually is a lot of places, but still not universal.

I could see something like Uber or Uber Eats trying to be early on something like this, since they already standardized the ordering for all the restaurants in their app. Scheduling systems are all over the place.