[jfengel]

If they set up their own shops, then they'd be far less visible, and they wouldn't benefit from the reputations that fairer dealers get.

Those "random corporations" are a few very large players who have won the network effect lottery. Most people will go to the place that everybody knows, especially if it's cheap. There's only room in the public brain space for a small number of these. It's very hard to set up a new one, especially if its tag line is "More expensive but at least it won't kill you".

Such natural monopolies are frequently subject to regulation if they won't do it themselves, simply out of self-protection. They're not just the "closest entity"; they're a bottleneck where regulation is feasible. But such regulation is going to be more cumbersome if it comes from an outside entity, so they should take calls like this as a sign that it will be worse for them one way or the other. Today, they've got some flexibility in their solution.