The point is to introduce this feature to those who may not have used it before. Everyone goes from not knowing about certain language features to knowing about them at some point. If you weren't aware of the language feature then this will clue you in that such a thing is possible.

Also many programming problems come down to just knowing the specific gimmic rather than finding it by problem solving. Usually that is some algorithm like fast prime calculation or efficient shortest path. You wouldn't be expected to derive Dijkstra's algorithm just by problem solving within a kata but those are still good problems that encourage you to research the solution.