Why can't i use a arrow function for the Checkstatus function?

const checkStatus = (response) => {
  if (response.ok) {
   return Promise.resolve(response); 
  } else {
    return Promise.reject(new Error(response.statusText));
  }
}

const select = document.getElementById('breeds');
const card = document.querySelector('.card'); 
const form = document.querySelector('form');

// ------------------------------------------
//  FETCH FUNCTIONS
// ------------------------------------------

function fetchData(url) {
 return fetch(url)
 .then(checkStatus)
 .then(res => res.json())
 .catch(error => console.log('Error found.', error))
}

Promise.all([
fetchData('https://dog.ceo/api/breeds/list'),
fetchData('https://dog.ceo/api/breeds/image/random')
  ])
.then(data => {
  const breedList = data[0].message;
  const randomImage = data[1].message;

  generateOptions(breedList);
  generateImage(randomImage);
})

// ------------------------------------------
//  HELPER FUNCTIONS
// ------------------------------------------
function checkStatus(response) {
  if (response.ok) {
   return Promise.resolve(response); 
  } else {
    return Promise.reject(new Error(response.statusText));
  }
}

const generateOptions = (data) => {
  const options = data.map(item => `
   <option value='${item}'> ${item} </option>
`).join('');
  select.innerHTML = options
}


const generateImage = (data) => {
 let html =` 
<img src='${data}' alt>
<p>Click to view images of ${select.value}s</p>
`;
 card.innerHTML = html;
}

const fetchBreedImage = () => {
 const breed = select.value;
 const img = card.querySelector('img');
 const p = card.querySelector('p');

fetchData(`https://dog.ceo/api/breed/${breed}/images/random`)
    .then(data => {
      img.src = data.message;
      img.alt = breed;
      p.textContent = `Click to view more ${breed}`
    })
}

// ------------------------------------------
//  EVENT LISTENERS
// ------------------------------------------
select.addEventListener('change', fetchBreedImage);
card.addEventListener('click', fetchBreedImage);


// ------------------------------------------
//  POST DATA
// ------------------------------------------