Why do we need to parse JSON for every person in the list people? Ist it not possible/more efficient to parse it once?

(...)
// Make an AJAX request
function getJSON(url, callback) {
  const xhr = new XMLHttpRequest();
  xhr.open('GET', url);
  xhr.onload = () => {
    if(xhr.status === 200) {
      console.log('Step 3: Parsin JSON to JS and callback');
      let data = JSON.parse(xhr.responseText);
      console.log(data);
      return callback(data);
    }
  };
  xhr.send();
}

// Generate the markup for each profile
function generateHTML(data) {

  const section = document.createElement('section');
  peopleList.appendChild(section);
  section.innerHTML = `
    <img src=${data.thumbnail.source}>
    <h2>${data.title}</h2>
    <p>${data.description}</p>
    <p>${data.extract}</p>
  `;
  console.log(`Step 4: creating DOM for ${data.title}`);
}

btn.addEventListener('click', () => {
   console.log('Step 1: Button clicled');
   getJSON(astrosUrl, (json) => {
      json.people.map(person => {
         console.log('Step 2: Iterating over people');
         getJSON(wikiUrl + person.name, generateHTML);
   });
});