<i>&gt;The DOS-style CLI arguments used by Microsoft&#x27;s other command line tools seem like such a stubborn throwback to a long-lost war. &quot;&#x2F;&quot; ... &quot;-&quot; ... </i><p>The reasons were technical[1] instead of a stubborn resistance.<p>The hyphen &quot;-&quot; was allowed in DOS&#x2F;Windows filenames.  The &quot;&#x2F;&quot; was not.  Therefore, if you programmed your command utility to use &quot;-&quot; as command line switches to match UNIX convention, your app would be &quot;broken&quot; because it couldn&#x27;t accept filenames that began with hyphens such as &quot;-verify.txt&quot;<p>If you then try to mitigate that with an &quot;escape&quot; switch such as double-hyphen &quot;--&quot; to turn off the hyphen processing, that means  you can&#x27;t operate on files that are named as &quot;--&quot;.  (Viruses and malware love creating files with legal filenames that utilities can&#x27;t open.)<p>So then you layer another hack on top of that and create the mother of all escape sequences with something like &quot;--switch_character=-&quot;  (and then cross your fingers that nobody has a file that&#x27;s actually named &quot;--switch_character=-&quot;.<p>(Arguably, you could make &quot;myapp -- --&quot; be unambiguous by imposing a rule that <i>position</i> is significant (the 1st &quot;--&quot; is parsed as a semantics switch, and the 2nd &quot;--&quot; is parsed as the oddly named file) but now you&#x27;ve given up the flexibility of specifying parameters in any order which many UNIX utilities <i>do</i> allow.)<p>Instead of all that complication, you just let &quot;&#x2F;&quot; be the switch character and it&#x27;s easier because &quot;&#x2F;&quot; is already an illegal character for filenames.  (When in Rome...[2])<p>[1]<a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;8.3_filename#Directory_table" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;8.3_filename#Directory_table</a><p>[2]<a href="https:&#x2F;&#x2F;en.wiktionary.org&#x2F;wiki&#x2F;when_in_Rome,_do_as_the_Romans_do" rel="nofollow">https:&#x2F;&#x2F;en.wiktionary.org&#x2F;wiki&#x2F;when_in_Rome,_do_as_the_Roman...</a>