In the medical space (at least in the U.S.), there's much less room for disruption relative to other markets. The market is significantly regulated / restricted; the law is structured so that even if the vendor and their potential patients both consent to a given transaction or procedure, the government can still step in and deny it.

In essence, the laws are structured under the (not necessarily wrong) assumption that the consumer is too stupid to identify snake-oil. All an incumbent has to do to block a newcomer to the market is make a hard-to-deny snake-oil accusation.