There's nothing magical about the medical field, that makes approaches developed elsewhere somewhat irrelevant there. It's just another fee for service arrangement. Although many Doctors do like to fancy themselves as special snowflakes.
There absolutely is something different about medicine: consumers' participation in the medical market is involuntary. We don't see doctors because we want to see doctors, we see doctors because if we don't, we will be maimed or killed by disease or dysfunction.
By the time people are seeking a doctor, they're often not in any position to evaluate the market--if a real market for medicine even exists where they live--and weigh the reputations or contractual demands of several doctors before choosing one. They're in pain, they're suffering, and they need a doctor now. That's very different than buying a watch on Amazon.
Heck, even someone rendering services as conceptually involuntary as a will executor, can have a reputation fr being good or bad. Despite you not necessarily having much choice on the matter when the headline service is being rendered.
This is mostly about exceptional cases.
The evidence that I see says that this has been a practice for at least five years, and according to the Boston Globe[2] one reason for this is that doctors feel like the conversation is one-sided, as they are legally forbidden from saying much about their patients.
1] http://boingboing.net/2009/03/05/doctors-force-patien.html 2] http://www.bostonglobe.com/lifestyle/health-wellness/2013/03...