The Atkins Industry has been wrong footed because of a basic error in the orginal concept of the diet.
At the time Atkins believed that it was fat which created a sense of fullness and satisfaction during ketosis, and this underpins the design of the entire diet and all the products, profits and investments in the company "Atkins Nutrionals" which depend on it.
Research in Scandinavia in the 1990-2000s proved pretty conclusively that the saiety came from protein, not fat; atkins worked, but by accident rather than design.
To admit that the Dukan diet is a legitimate effective low-carb low-fat alternative would undermine the Atkins concept entirely.
To give you some idea how cynical of the marketing of Atkins products are - the company Atkins created is now owned by a group which also owns fast food chains like 'Auntie Anne's' (fresh sweet pretzels), 'Carvel' (ice-cream and ice-cream cakes) 'Cinnabon' (large danish pastries with thick sugar icing), 'Moe's Southwest' (Tex-Mex), 'Schlotzsky's' (American sandwiches) 'McAlister's' - filled baked potatoes, and 'Wingstop' (fried chicken wings).
They own no other 'health', 'medical' or 'wellbeing' products.