Fields requestor, assignment group, assigned to are not visible to other users (than admin) on a form. Admin user can see the fields on the form.
The fields requestor, assignment group, and assigned to are fields the referenced to user(sys_user) and groups (sys_user_group) table. If the users does not have access to User/Group table, then the referenced fields from the User/Group table will not be visible to such users on the form.
Create the necessary Read/Write ACLs on Group(sys_user_group) and User(sys_user tables) to grant access to other role users than admin.