Iit may be easier to eliminate sugar first and then move on to starch
It makes sense. Psychologically speaking, I suspect it is much easier for people to give up on sugars than carbohydrates.
We've known for a long time that high sugar consumption isn't healthy and most people have, at one point or other, tried to stay off sweets. They are familiar with the concept and how it feels.
On the other hand, we had drummed into us how we should build our diet around "healthy" carbs. Greatly reducing or even entirely giving up on bread, pasta, rice, potatoes, is less common and a heavier commitment. For many it would be like navigating uncharted territory.