No idea if this is intenional or if it was just for the drag space / design, but what it also does, is that it moves the start of the URL more into the middle of the viewing area.

And the start of the URL contains security-critical information (http/-s and domain name), so having that closer to your eyeballs is generally helpful, even if it means cutting some of the URL off at the end. Especially so for average users which is ultimately the user group that's mainly going to be using the default.

Since on most platforms the tabs go all the way to top of the window now, there isn't room to grab the window to move it around. Those spaces act as extra drag targets.