Perhaps it would be better: Why can’t chess be solved yet?
And the answer is because today it is still beyond our abilities to develop the appropriate algorithm.
I frequently read figures, which I am not quite sure how they got, where they indicate that the number of possible moves is greater than the atoms in the universe and that due to this complexity there is no current computer that can calculate all possible moves and develop the appropriate algorithm. They even talk about quantum computers and the like.
Well, I have news for you. Chess engines have been used since time ago to calculate all possible moves in some simple endings and generate endgame tablebases containing all possible positions. Yes, all. And you know what? Chess engines continue to use endgame tablebases because no one has been able to develop an algorithm to replace them.
That simple.
Note that this is page 669