Can we make Conversion date non-mandatory on sales orders when currency conversion type is 'User'?

When currency conversion rate type on the sales order is Corporate or any other date based conversion type, it is understandable that a conversion date needs to be provided. But when the conversion type is 'User', the user manually enters the conversion rate. So why does the system insist on a conversion date? Is there a way to proceed with order booking without the conversion date when the type is User?