This is a really interesting case of Emacs being so old that its default (and only in this case) behavior is just unable to comprehend current computer technology and usage. I think I am correct in saying that the lack of capabilities to have horizontal scrolling of a screen was an absolute hard limit of the teletype and terminal era. It should not be difficult to add such capability, but more than the obviously connected portions of Emacs’ code could implicitly rely on the assumptions that come from the impossibility of horizontally extending text.