Here is the really short primer on copyrights. Copyright protection requires originality and fixation in a tangible medium. Originality means that the work must be individually created by the author and involve some degree of creativity - in otherwords, it can't be an exact copy of something already in existence. You're right, a lot of dancing does seem to be just different ways of combining the same turns that people have been doing for years. The mere fact that the turns are done in a different order makes the dance original.
Copyrights protect the tangible medium only.
Copyrights do NOT protect facts, ideas, procedures, processes, methods of operation, concepts, or principals which are embodied in the tangible medium. However choreographic works may be copyrighted and one of the protections of copyright is the exclusive right of public performance of certain types of works and this specifically includes choreographic works. First, the protections of copyrights are severable - you can waive one or more of them while retaining the others. Consider the line dance choreographer - in order for their work to become well known and for them to make money off of it, the dance has to be performed by others. Fair Use is use techincally forbidden by the law, but allowed where it is reasonable to assume that the author must have foreseen it and consented to it.