Because the law does not operate that way.
It's a big question you ask - they design and manufacture products and sell them in bulk to distributors or to direct vendors.
People buy the products from the vendors and the individual vendor holds the responsibility for any warranty - the manufacturer is disconnected from the contract you have with the vendor. The vendor is not in the least interested in selling replacement bases to repair kettles - the vendor just wants to sell more kettles - not spare parts for kettles already sold. Similarly the manufacturer is not bothered much by the spare parts business - little opportunity for profit there.
So you see - the manufacturer has no contract with you and doesn't care much for your views - not once you've bought the product. The vendor wants to keep things simple and will offer you some kind of warranty as required by law.
You might speak to your political representative about getting the law changed with respect to replacement parts for kettles but I somehow doubt that you will be taken very seriously - not enough votes in it - kettles do not feature in any political manifesto as far as I know.
If it's a stand-on plinth for your kettle that's broken - they are usually easy to dismantle - there's not much in them to go wrong - no problem for the average handy-man.
Good luck...
Peccavi
April 2013