"Why can't I see an SO Type in the SO List?" or "How can I restrict non-admin users from seeing certain SO Types?"

From the User Setup window, you can restrict or grant access for non-administrative users to certain SO Types. 

To do this, go into the menu Admin > User Setup > SO/Job Types

In the User Setup window, highlight the DBA user name you wish to change the permissions for, then go into the SO/Job Types tab.  In the SO/Job Types tab, you will need to check or un-check the SO Type you wish to grant access to or restrict access of based on the DBA user you have highlighted in the main User Setup list screen.

After you have made these changes, the user should only be able to see the SO Types they have access granted to.   

However users with administative access to DBA are automatically granted access to all SO Types.