I think there are several backend ranking metrics for which thanks could be useful… Say as a ratio of "answers to thanks" to help identify reputation/non-spamminess in a given user's contributions on-site. Such a metric could help people skip over initial moderation queues or post per day limits faster, or affect the weighting of their own up/down votes somehow.
As a straight upvote, I'd agree with Vicky Stringer, what's the point? If you can do both separately, there's no need to combine them… And whether it is simply as a gesture, or as a subtle means to suss out high quality participants, Thanks has clear extant or potential use cases that obviate the need for its elimination.
