Why can buyers still leave feedback after cancelling a purchase?

[ntomntom]

Recently sold an item on ebay and issued an invoice.  I had no contact from the buyer after 3 days so sent a message (politely) asking if they intended to pay.  They replied saying circumstances had changed and they didnt want it any more -it was just before Christmas so I guess they found an alternate present!!  So I cancelled the transaction to get my seller fee refunded.

I then had negative feedback from the buyer saying I was "unhelpful" in the comment.  

Now I have successfully appealed this, so full marks to ebay for that, but why should buyers be able to leave feedback if they request a cancellation?

It would appear I can bid on anything I like.  Change my mind and not pay.  Then leave negative feedback for the seller.  I can see no valid reason to allow feedback to be left in these circumstances.  If I refuse to pay, why should I be able to leave feedback?

EDIT:

To be clear, I have just checked & actually I did open an Unpaid item case (rather than cancellation).  And it has been settled.

My issue is the fact that the buyer was then able to leave negative feedback.

Why would the system be designed in this way?  Credit to ebay the negative feedback was removed when I raised it, but why should I have to spend time chasing this when the system should not have enabled the buyer to leave feedback under these circumstances.

[m25jet]

In cases such as this if the buyer doesn't contact you first of all within an acceptable timeframe and politely request a cancellation of the transaction then the best option is to open an Unpaid Item Dispute against the buyer.  If the buyer has still not paid for the item after four days then close the case down, making sure that when the question "Did this buyer pay for the item?" appears on the screen you tick the "No" box.  That way your eBay Final Value Fees will be refunded, although you won't receive a refund of PayPal's cut of the sale, and the buyer's account will be hit with an Unpaid Item Strike.  If the buyer picks up two or more Unpaid Item Strikes within a twelve month period then he or she will find it almost impossible to purchase anything on eBay, in which case it should also prevent the buyer from wasting any other sellers' time.

If you have not already done so add the buyer's User ID to your Blocked Bidders List.  To access your Blocked Bidders List click on this link https://offer.ebay.co.uk/ws/ebayISAPI.dll?bidderblocklogin and a big white box will appear on the screen.  Add the buyer's User ID to that white box, click on the Submit button beneath it and once you have done that the buyer in question will not be able to purchase anything else that you list for sale on eBay in the future, in which case he or she will not be able to cause you any further aggravation.