Because postage and delivery charges are calculated based on where you are the cart needs address information to calculate this.
Even within UK postal code area’s this may vary as couriers have different charges for larger items sent to the Islands and Ireland.
The good news is that you can calculate this easily once you have added the parts to the cart.
Simply select your county or state and if in the UK your postcode and select ship by weight and update shipping and handling charges and the total including delivery will be displayed.
Note VAT will not be including until you reach the final checkout pages. VAT is charged at current UK rates.