I saw these all over South Jersey, but never anywhere else. Do you know what it is for? I have no clue:
https://www.google.com/maps/@39.9031352,-75.0745643,3a,24.2y,355.11h,81.05t/data=!3m6!1e1!3m4!1sCclTDFh21xfGQjs4a7pc4w!2e0!7i13312!8i6656
My guess is that it's a sewer vent pipe.
That would make perfect sense. I'm going to assume you are correct.