Earlier quoted context omitted.
It's about the principle. www is a valid subdomain. Browsers are supposed to be as unopinionated as possible since they are browsers , not mediators, and their job is to implement the standards of the web.
Your opinion that browsers should be unopinionated is not an opinion shared by browsers.
* Chrome encourages you to sign in to the browser with a Google account.
* Firefox's new tab page shows stories and articles from Pocket.
* The news feed shown by default in Edge provides stories from MSN.