I suffered from this for over a decade and a half.

Why is it the medical professionals are avoiding dietary changes?

Only one doctor is all those years recommended dietary changes. I ignored this doctor for 2 years thinking it was silly or that she was a crackpot and yet kept the idea in the back of my mind. I wanted a pill or a prescription. Most prescribed the topicals like in this video, which helped me not at all and in fact often exacerbated the symptom's. One gynocolgist said he found nothing wrong with me it was in my head, another said it was heat rash and prescribed a compounded steroid! I saw at least 6 gynocolgist's over the years getting nowhere. Out of desperation I began an anti-inflammation diet. Maybe that crackpot doctor was right. I read The Yeast Connect Handbook, by William Crooke Md. This explained how yeast which is living in our body raises our inflammation leading to many diseases. Mind you, I had been swabbed for yeast, had no discharge and no external evidence of yeast was found. Looking back I now know how swollen and red my vulva was, today it is not enlarged and is a darker in some areas and more flesh-like in color lacking the redness. This diet plan gave me some relief beginning in 6 weeks and by 2 months I was pretty sure it was working as the yeast colonies living in the colon die out. The detox period for this diet is 2 months, but I kept it up for 3 months. It is brutal, you will want to eat forbidden foods like Processed Sugar, but I would tell myself, "When will you learn, it's going to make you burn." and pass it by. In three months I was almost itch and burn free, but still had some sensitivity. Yet gone was the feeling like I had acid poured on my vulva and into my vagina. I have followed the maintenance plan of this diet fairly closely for 3 years now and never think about burning itching or pain and have normal, pleasurable intercourse. I do eat several serving of fruit, natural sugar a day and allow myself one meal including a gluten carb and am still fine. Yet zero processed sugar for life. Processed sugar is the fuel that immediately is passed to the yeast in your intestines. If you take that away from the yeast they scream at your brain, "Feed me something sweet, I want sugar", your mouth will salivate simply thinking about sugar. You must be as miserable as I was to attempt this, for me pain is a serious motivator.