Some fields/columns are not available to show in Request list

Some fields/columns are not available to show in Request list

Hi
 
Some fields are not appearing in the Column list when choosing to adjust the Request list. They are available to select for Technicians but not for Requestors. If I open an individual Request, the field is available to view in the Request form. However, I cannot select it to show it on the filtered view list of Requests.
 
Thanks