I have 2 set of codes part 1 and 2.Can i know why part 2 uses return listHTML; and not print(listHTML) like part 1?

var playList = [
  ['I Did It My Way', 'Frank Sinatra'],
  ['Respect', 'Aretha Franklin'],
  ['Imagine', 'John Lenon'],
  ['Born to Run', 'Blue Springsteen'],
  ['Louie Louie', 'The Kingsmen'],
  ['Maybellene', 'Chuck Berry'],
];

function print(message) {
  document.write(message);
}

function printSongs( songs ) {
  var listHTML = '<ol>';
  for ( var i = 0; i < songs.length; i += 1) {
    listHTML += '<li>' + songs[i][0] + ' by ' + songs[i][1] + '</li>';
  }
  listHTML += '</ol>';
  print(listHTML);
}

printSongs(playList);

var questions = [
  ['How many states are in the United States?', 50],
  ['How many continents are there?', 7],
  ['How many legs does an insect have?', 6]
];
var correctAnswers = 0;
var question;
var answer;
var response;
var correct = [];
var wrong = [];

function print(message) {
  var outputDiv = document.getElementById('output');
  outputDiv.innerHTML = message;
}

function buildList(arr) {
  var listHTML = '<ol>';
  for (var i = 0; i < arr.length; i += 1) {
    listHTML += '<li>' + arr[i] + '</li>';
  }
  listHTML += '</ol>';
  return listHTML;
}

for (var i = 0; i < questions.length; i += 1) {
  question = questions[i][0];
  answer = questions[i][1];
  response = prompt(question);
  response = parseInt(response);
  if (response === answer) {
    correctAnswers += 1;
    correct.push(question);
  }else {
  wrong.push(question);
  }
}

html = "You got " + correctAnswers + " question(s) right."
html += '<h2>You got these questions correct:</h2>';
html += buildList(correct);
html += '<h2>You got these questions wrong</h2>';
html += buildList(wrong);
print(html);