There's that, and there's also compliance - if your doctor tells you you should become a vegan ultramarathoner, chances are you will probably not comply; if the

There's that, and there's also compliance - if your doctor tells you you should become a vegan ultramarathoner, chances are you will probably not comply; if they tell you to take two pills every morning, you may still not, but the chances are at least better (even if the improvement is also less significant).