Well the feedback link is given to all users whom have purchased from a user in an auction which is the whole point of the feedback.
The user who was the high bidder recieves the link to give feedback. We can certainly add a link but that would give users the ability to add bad info when they never bought from the user. Only user's whom won a product at auction get this link. Now I can place a link in the buy it now email that goes out for regular classifieds