Why does this work and this does not React?

Question

React

// Это сохраняет и работает
state = {
        user: false
    }

    componentDidMount() {
        fetch('http://localhost:3000/auth/login')
            .then(res => res.json())
            .then(res => this.setState({user: res}))
            .then(() => console.log(this.state.user))
            .catch(e => console.log(e))
    }

// Это не сохраняет в user и не работает
const [user, setUser] = useState({})

useEffect(() => {
 fetch('http://localhost:3000/auth/login')
            .then(res => res.json())
            .then(res => setUser(res))
            .catch(e => console.log(e))
}, [])

Answer 1

Why should this work if you don't use the user variable in the hook example?