jQuery がパスワード入力フィールドのタイプを変更できないのはなぜですか?

$(document).ready(function() {
    $('#password').attr('type', 'text');
    $('#password').val('Password');
});

// We can't allow the type property to be changed (since it causes problems in IE)
if ( name == "type" && jQuery.nodeName( elem, "input" ) && elem.parentNode )
    throw "type property can't be changed";

var pass = document.createElement('input');
pass.type = 'password';
document.body.appendChild(pass);
pass.type = 'text';
pass.value = 'Password';