a ground sleeper won't pitch their tarp into a steep a-fram in high wind, whereas the hanger will, this puts more loading on the fabric.

i think maybe you're looking at one brand (oes) and then lumping everyone else in the same boat. i'd say most hammock tarp brands aren't using edge binding around the peremiter. my tarps for instance have a rolled-hem along the peremiter, and edge binding on the ridge seam (which is no heavier than a flat felled seam with seam-sealer applied) then grosgrain for the corner attachments.