as an american culinary certified chef and over 20 years as a chef i am sorry that you feel like no one in the profession will give you an answer.
the answer is very simple and is only comprised of one word and that word is "economics"
now i know this seems simplistic and on the face of it it is but bear with me.
think about the biggest economic factor that can affect anyone in food service. that factor is litigation.
i worked for 15 years in the conference and convention field. i studied on my own time and took courses for special diets and to be honest loved doing them. thats the good part. now for the bad part and that is the customer. to protect ourselves special dietary plates were taken out by our most trusted server to ensure proper delievry of the product to the customer. so far so good but we went one additional step to protect ourselves in the event of a lawsuit over not delievering a special diet meal. that server watched the customer. if the customer attempted to take food items not sent to him or her (called plate sharing) the server would advise the customer against it reminding them of their special dietary requirements. the server would then log down the table number and time which could be crossed referenced for our lawyers use if needed.
now here comes the really said part and for me it was sad since i really enjoyed the challenge of making good food taste good when there are so many restrictions.
IN 90 TO 95% OF THE CASES THE SPECIAL DIETARY CUSTOMER IGNORED THE SUBTLE ADVICE OF THE SERVER WHICH WAS GIVEN AS A VERY POLITE REMINDER TO STAY ON THEIR DIET AND WENT AHEAD AND ATE FOOD FROM ANOTHER PLATE!!!!
in a nutshell that is why you are going to be hard pressed to find the special diet you need.
sorry but it's the truth
but on a happier note special diet people were better than the vegatarians if that is any consolation