I can't really explain "why" they continue to push misinformation, except that medicine is largely based on precedent and consensus, and that even desperately needed change is slow. Once standards become institutionalized, they're hard to change, and doctors are eager to follow established practices even when they know that they're probably wrong if only to prevent lawsuits.
And maybe I'm wrong, but I've had a number of doctors over the past few years who have given me the impression that they just think I'm hopeless. I've kept my A1c below 5.5% the entire time, I've taken my medication, I've never skipped a doctor's appointment, and I've lost ~100 pounds, but for some reason they treat me like complications are inevitable and diabetes will shorten my life.
In short: they're managing me, keeping me alive right now, not trying to help me live as long as I would've without diabetes. I suspect they think it's a foregone conclusion that I will die younger and that I have to be unhealthy, so rather than assisting me in tightly controlling blood sugar and supporting my diet (a diet they believe is questionable in the first place), they'd rather just help me avoid dying in my sleep of low blood sugar.
Sadly, these diabetic forums are full of people who are unusual because of how much they care and how hard they work. Doctors don't see diabetics like us often enough and then the poorly controlled diabetic becomes a reinforced stereotype. They give bad advice, their diabetic patients are uncontrolled and sick, therefore all diabetics are uncontrolled and sick and nothing can be done.
My doctor saw my BG log, told me that I had the best blood sugar he'd probably see in a diabetic in the next ten years (huh?), and then talked to me about how I didn't have kidney damage because I haven't been diabetic long enough. I'm like, do you even know what causes kidney disease in a diabetic?
