Customer feedback emails missing the point?

Does an email after a completed purchase mean a positive customer experience?  Sure it may help the next customer but how does it improve the experience of the purchaser giving the feedback?  The chance to win a voucher to incentivise you to give feedback is one way but only really rewards the handful who get the gift. Is there more opportunity in the trip advisor model where you receive updates on how valuable your feedback has been?  If you could rate the value of the feedback so customers remain connected to their feedback you build a stronger relationship. You could in turn identify the customers whose opinions matter and work to use these customers for new product launches and to do soft testing of changes.