"Why shouldn't cruising sailors be interested in improving the performance of their boat?"
Perhaps cruising sailors are quite happy and content with the performance of their boats as they are. Perhaps all they want to do is to sail gently, sedately and safely without putting any more stress or strain on the boat and its rigging, and if it takes a bit longer to get from one point to another, the benefit is in taking part rather than trying to arrive first. Each to their own, but for those that want such a chart, good luck. I hope you find what you want, but while I'd be interested to see what information can be gained from such a chart, I won't be upset if I never see one.