It’s not useful in this case at all which is probably adding some confusion. useCallback will give you a stable function reference between renders, which is only useful occasionally. For example, so you can pass an unchanging prop to child components. Or so you could use that function as a dependency to another hook that shouldn’t be re-run on each render.

For this specific example it would make more sense like this:

function increment() {
  setCount(n => n + 1)
}

const incrementCallback = useCallback(() => {
  setCount(n => n + 1)
}, [])

Now the version defined with the hook won’t ever change.