Hi,
There is no setting to select the language the shop owner will receive the emails in.
So that's the main reason.
However, there is a mechanism to send the emails to the customer in their own language.
Now what you can do is edit the "order admin notification" and "payment notification" via the menu System>Emails and add such code at the top of the preload section of the email:
<?php
$orderClass = hikashop_get('class.order');
$lang = new stdClass();
$lang->order_lang = 'en-GB';
$orderClass->loadLocale($lang);
?>
and that will force the language of the email to be english (or whatever language you want if you replace en-GB by another language code).