Earlier quoted context omitted.
We do that with "almost everything"? I can't think of anything. I don't think e.g. phone service is comparable, because while you might not pay when the service is down, the service's uptime doesn't depend on you. If you destroy your cell phone, you can't use the service, but the service is still working. If you sold "medicine as a service", it would just include that, but it couldn't guarantee that you'd always be h…
Sure we do, as soon as anything degrades or completely stops working, whether a product or service, we ditch it and/or it is worked on until it's fixed. Whereas with medicine, people will sit there and let the system slowly and agonisingly fail them over and over again, at tremendous personal expense, until they are literally dead. Medical malpractice - that is, a medical professional getting their treatment provably…
So do humans. But sometimes both of them stop working, or some part of them stops working. The service provider will not care if you break your cellphone, they only provide the cell service.
The problem with the idea of "you pay a flat fee for your health, and someone else makes sure you're healthy" doesn't work unless you also give them control over most of your life: what and how much (and when?) you eat, when and how much you sleep, any other substance you (ab-) use, what and how much physical activity you engage in. But who wants that?
Malpractice is a serious issue, but it won't be solved by "payment on success only", you just won't have anyone take on cases that are somewhat complicated, and then litigate forever to define what "success" means.