The default Values for Field Level Security and Auditing for the Attributes in MS CRM 2011

just the below observation in ms crm 2011 respect to the 'Field Level Security' and 'Auditing' ...
when we create the attributes or the system attributes the default values for the ablove two are different ...

1. for custom attributes...(except lookups created by N:1 relationship)...

Field Security : Disabled
Auditing : Enabled


2. for System attributes...(like createdby, createdon etc)...

Field Security : Disabled
Auditing : Disabled


3. for custom attributes...(lookups created by N:1 relationship)...

Field Security : Disabled
Auditing : Disabled

Regards,
yes.Sudhanshu