You'd think, but the government has the habit of getting involved. Usually some politician in a given state will make a stink about some perceived inequity, ram-rodding legislation through to right said perceived inequity. Warm and fuzzies to all involved, everything is sweetness and light. In the past similar stunts along these lines has caused companies to pull completely out of certain states. "If that's the deal, we'll just leave, no thanks."
The government's answer to this angle is to *force* insurance companies to provide coverage (at reduced rates) to those who wouldn't get written in the first place.