Some doctors will. Most will still refer you to a dietician after your initial diagnosis of diabetes. Most (not all) dieticians are still sold on the ADA diet which is much higher in carbs than is good for most diabetics. Since a lot of folks are way high on carbs in their pre-diabetic days, the ADA diet is a reduction (150-200 grams of carb per day) and they may appear to be doing well with diet control...for a while. Then their blood sugar control starts to get worse and eventually gets out of control. This is exactly what happened to me. I think this is why so many doctors expect their patients to get worse; first moving to oral medications and then eventually needing insulin. What amazes me is that they consider this the "normal" progression of the disease instead of thinking that maybe it could be avoided by changing a person's diet.
Diabetes by nature means that the person has a problem with carbohydrate metabolism, more than likely complicated by some degree of insulin resistance. It doesn't make sense to me to take a person who already is having problems metabolising carbohydrates and instead of telling them to cut back on those, tell them to cut back on proteins and fats instead and only cut back on carbs a little.
Would I have switched to low carb sooner had I known 10 years ago what I know now? Yes! But instead it took my blood sugars going out of control and winding up on oral medications (along with developing high blood pressure) to convince me that there was something wrong with what I was doing and it needed changing.
I work with a lady who went directly to insulin control when she was diagnosed with diabetes and has multiple health problems on top of it. I loaned her my book (Dr. Bernstein's Diabetes solution). She read it, gave it back and said she'd stick with the recommendations of the diabetes clinic (the ADA diet that failed me so miserably). You can lead a horse to water....