Use shipping Code to calculate freight option

When setting "Use shipping code to calculate freight" to Yes, when we print our sales orders the ship via prints.  When it is set to No the ship via does not print on the sales orders.  I did look at dbo_SO_SalesOrderHeader and the ship via does not save when it is set to "No" either, but it does get saved when it is set to "Yes".  I guess I don't under stand how calculating freight should stop information from being saved with an order.  If you are doing an order that is shipping with a trucking company you would still want to know how it is shipping on the paperwork.  We even had a UDF to store the description for the Shipvia so we could print that on the order too.  We would like to have the option set to No so when you do go back into an order it does not delete any freight you might have already entered.  We can not set it to No right now because then we get no information.  Hope all that makes sense.