I can find countless quotes like this
In many countries chess is incorporated into the scholastic curriculum. Countless researchers and studies have shown over the years that chess does indeed strengthen a child's mental clarity, fortitude, stability, and overall health. In this technologically driven world, chess helps aid in the synthesis and growth of certain areas in the brain and mind where many children can benefit as they grow older from the game. "It's all condensed in a playful manner in a game format and it's extremely fascinating because first of all I'm in control of my own destiny, I'm in charge. You have to be responsible for your actions, you make a move, you had better think ahead about what's going to happen, not after it happens, because then it's too late. Chess teaches discipline from a very early age. It teaches you to have a plan and to plan ahead. If you do that, you'll be rewarded
These beilefs are so strong that even got a recognition in Wikipedia.
Here is another quote to highlight the gist of my question
Chess has a unique and strong brand attribute, in that it is generally perceived that playing chess and being smart are connected.
I do not ask if chess really improve the mental performance. I am asking
Why are they considered unique/unmatched in this respect? Almost any game demands strengthening your intellect for careful planning of your moves. Why other games are less useful?