Why call enableSubmitEvent()?

//Problem: Hints are shown even when form is valid
//Solution: Hide and show them at appropriate times

var $password = $("#password");
var $confirmPassword = $("#confirm_password");

////Hide hints
//$("form span").hide();

function isPasswordValid () {
  return $password.val().length > 8;
}

function arePasswordsMatching () {
  return $password.val() === $confirmPassword.val();
}

function canSubmit () {
  return isPasswordValid() && arePasswordsMatching();
}

function passwordEvent () {
  //Find out if the password is valid
  if (isPasswordValid()) {
    //Hide hint if valid
    $password.next().hide();
  } else {
    //else show hint
    $password.next().show();
  }
}

function confirmPasswordEvent () {
  //Find out if password and confirmation match
  if (arePasswordsMatching()) {
    //Hide hint if matched
    $confirmPassword.next().hide();
  } else {
  //else show hint
  $confirmPassword.next().show();
  }
}

enableSubmitEvent () {
  $("#submit").prop("disable", !canSubmit());
}

//When event happens on password input
$password.focus(passwordEvent).keyup(passwordEvent).keyup(confirmPasswordEvent).keyup(enableSubmitEvent);

//When event happens on confirmation input
$confirmPassword.focus(confirmPasswordEvent).keyup(confirmPasswordEvent).keyup(enableSubmitEvent);

enableSubmitEvent();

$("form span").hide();