setCart hooks during codeacademy lesson: adding objects to Arrays,

I’m working on State Hook, where we are adding objects to an array (https://www.codecademy.com/courses/react-101/lessons/the-state-hook/exercises/arrays-in-state).

I noticed that the code below adds an object to an array by setState.

const addItem = (item) => {
    setCart((prev)=>{
      return [item, ...prev];
    }) 
   };

But i’m wondering why return is inside the setCart function, while it seems more logical to return the entire setCart to addItem.

I got confused because in the previous lesson, I learned changing the variable or function should be done by returning the entire function, like this:

  const goToNext = () => {
    return setQuestionIndex( (prevQuestionIndex) => prevQuestionIndex + 1);
  }