[NearAP]

My opinion leans towards - they considered the use-case but ruled it as uncommon and so didn't design for it (or pushed it down the priority queue). This is because it seems that most people in the US (at least those with smart phones) are on some form of contract rather than use a pay-as-you go; it also seems to me that those on contract would most likely retain their number even when they move (within the US).