If there was no value provided to customers, then why are people in this thread so angry? They're angry because something valuable they used to get for free now requires money!

Standing up your own registry is trivial at the kind of scales (dozens-to-hundreds of images pulls per day!) that we're talking about. It's just expensive, so people want Docker, Inc. to do it for free. Well...

Because it's a classic EEE-style technique. You force (or very strongly encourage) customers to use your system instead of any competing system. Then, only when all the customers are using your system, and all the competitors are out of business because they don't get customers any more, you rug-pull the customers for money. This wouldn't be a problem if you always had to specify a system when pulling an image, because Docker would be on equal ground to everyone else.