Accepts are a way to indicate what worked best for the OP or which answer they personally liked. Sometimes the OP's choice isn't the best one - after all, many people ask questions because they don't know much about the topic, so they can't necessarily be expected to be a good judge. Also, sometimes better answers are posted later after the OP has stopped interacting with the question or no longer has the ability to test solutions.

The score of a post gives a more reliable indication of its quality, as potentially more (and possibly more knowledgeable) people are involved in determining it.

Therefore, I think we should have the accepted answer sort according to score, rather than being pinned to the top.