You’re right and there are some provider segments like MRIs that have succeeded with this model.

From our perspective the real blocker is the “lock in” due to timing and the referral process. We’re paying bills to providers like specialized labs that are 2-3 degrees down the chain from our doctor (e.g. radiologist refers pathologist refers lab1 refers lab2 – we only see radiologist) .

Even if there was a “amazon for labs” we wouldn’t be able to order this stuff because the decision is 2 degrees away.

Fun fact is that most such obvious innovative solutions are prohibited by law. There are many layers of turtles the lowest two are: corrupt politicians and, population that doesn't care about corrupt politicians.