There are plenty of tools to automate that. arandr is a very simple and powerful tool to arrange monitors with a GUI. Gnome has its own, much simpler, monitor configuration dialog. My system defaults to extending to the right, by the way, because that's generally what I want when connecting a projector.
None of this is new, and the whole point of this discussion is that Linux desktops are much better than they were ten years ago. It is that old state that many folks have in mind when criticising Linux distros' usability. It's just not a very interesting discussion to have.
And the thing I think you're hearing is that "progress" should not equate to "good enough." Doing a sensible and even helpful thing by default is part of user friendliness.
None of this is new, and the whole point of this discussion is that Linux desktops are much better than they were ten years ago. It is that old state that many folks have in mind when criticising Linux distros' usability. It's just not a very interesting discussion to have.