Based on my personal experience, my guess would be for the same reason I stopped using Western Medicine back in 1981: too many medical mistakes, misdiagnosis, false positive tests, negative reactions to drugs, irresponsible drug prescriptions and a propensity to manage disease rather than heal the person.
After I left Western Medicine I learned what it takes to be healthy, including cleaning up the air I breath, the water I drink, bathe in and cook with, the food I eat, the electrosmog I expose myself to, the thoughts I keep, the words I speak, the actions I take and the friends I spend time with.
Sickness comes to those who are frequently stressed by one or more of the above, so anyone wanting to get healthier must begin the process of weeding out all those aspects of life that do not promote greater health and replacing them with new elements that encourage a healthier body, mind and spirit.