useActionState Required to Return Data From a Server Action

Server Actions can return any value directly, and the client component can read it as the resolved value of the async call with no additional setup.

A Server Action's return value cannot be read directly by the calling component because the call crosses a server round-trip outside React's normal render cycle; the response must instead be threaded through useActionState (formerly useFormState), which re-renders the component with the action's result once the round-trip completes.

Server Actions are void functions by specification and can never return anything, even internally.

The return value is available directly, but only inside a useEffect that polls the action's internal promise.