The subdomains are hidden, so that less people get fooled. Most people will only look at the left-most part of the URL to see what website they are on, and hackers take advantage of that.
I would hate that "feature" in my browser. I like being able to see the subdomains, and my screen is big enough to highlight an unexpectedly long URL. It could be useful on small mobile screens though.
I'd hate it too, but there is no default configuration that satisfies everyone's wants at once. That's why I said there should be a settings option to toggle showing everything in the URL.
I already dislike how Chromium hides the "http://", which only pops up when I click to edit (and then moves the entire URL to the right).
Chrome developers have decided that for "aesthetic reasons" that they should not allow this and other settings to be configured.
I mean there are many ways you can implement a trap door where you can enable "minimalist" and "advanced" settings, without cluttering the settings dialog itself (chrome://experiments, command-line options, config files, the list goes on). That's a pretty narrow-minded design decision if you ask me.