Reference Fields like 'Requestor' (a reference to sys_user table), 'Assignment group' (a reference to sys_user_group table), 'Assigned to' (a reference to sys_user table) are not visible to non-admin users (than admin) on a ServiceNow Form.
However, all 'admin' users can see these fields on the form.
Release or Environment
These affected fields like 'Requestor', 'Assignment group', and 'Assigned to' are referenced to user(sys_user) and groups (sys_user_group) table. If the users do not have access to the 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 so that the non-admin users can have access to these fields on the forms.