Why is a maize grain usually called a fruit and not a seed?

(N/A) maize grain is technically a fruit because it develops from a mature ovary.
In maize,the fruit wall (pericarp) is fused with the seed coat to form a single unit.
This specific type of dry,indehiscent fruit is known as a $Caryopsis$.
Since it contains both the seed and the fused fruit wall,it is botanically classified as a fruit rather than just a seed.