Why does shipping/tax stay the same after applying a gift card to the order?

Why does shipping/tax stay the same after applying a gift card to the order?

In its essence, a gift card is different from a discount coupon. A discount is applied to the product(s) in the order, changing their final price. Thus, Magento recalculates tax and shipping rates to correspond with the changed final price of the product(s). 

A gift card, in its turn, is not applied to the products' price but rather to the order total. The order total may or may not include tax, shipping, previously applied discounts, etc. A gift card can cover tax and shipping, but doesn't trigger their recalculation. 


      
When the gift card code is applied, shipping and tax costs do not change, but the subtotal is recalculated.