Vapor barrier over interior CMU piers in a crawlspace-what is the point? – GreenBuildingAdvisor

In online photos and in actual crawlspaces that have been conditioned I mostly see the vapor barrier run to the top (or with termite inspection gap) of interior CMU piers, three/four feet above the ground surface.  Why is this done?  Code only requires it be run up the foundation walls 6″ in my CZ3A.  Is wicking the reason?  I never see this discussed.

Thanks for any insights.  Jeff