It is 100x easier to support your own software. If the default browser breaks for some reason, it often just feels like the OS broke to the end user!
Microsoft would love to remove the option to choose a system default browser entirely, but they can't, so tactics like these are the next best thing. That's just how big the difference is in supporting foreign software vs. a first-class package you can hook into.
Then they should issue a Windows Edge Edition that boots directly into Edge. Honestly, today everything runs in the web, so you might as well use just the browser.
