Or maybe they just thought AT&T had really crap reception wherever they went?
Admittedly that's a flippant remark but I still haven't seen any indication as to what proportion of users are having the problem. It's getting press because it's Apple, not necessarily because huge proportions of users are having issues. I expect someone here will correct me if I'm wrong though.
most likely, the reason being that they field-tested this whole thing with 3gs look-alike dielectric (non-conducting) case...