I hear where you are coming from but was it in his job description! People have been fired in the past because they were doing so many extra tasks that the reason they were hired in the first place fell by the wayside. Their performance review was not based on what the did but on what they should have done.
On the other hand, if you do a good job and a lot of other things because you have extra skills, you will not be seen by management as an indespensable employee but as the sucker they can always trust to go the extra mile for no extra money. These people often head for a burn-out.
At my school, we had a guy who knew computers. BUT... he wouldn't improve our network/system unless the company paid him extra (even in regular hours he wanted overtime). Result? Nothing got better for twelve people because one !$%*!$% wanted to avoid extra work.