I do suspect a likely reason is because while secure FTP protocols exist, they are often not well-supported by both servers and web browsers alike. So while FTP

I do suspect a likely reason is because while secure FTP protocols exist, they are often not well-supported by both servers and web browsers alike. So while FTP can be secure, the implementation in practice often is not, and Firefox and Chrome are both pushing a "literally everything over HTTPS" mentality. (I have significant reservations about this concept, but in a world where they're shoving your DNS requests through HTTPS, it isn't surprising they are also want file transfers to be through HTTPS.) You can see here where the GUI didn't support FTP over SSL, and then eventually got marked WONTFIX because they decided to deprecate FTP entirely instead: https://bugzilla.mozilla.org/show_bug.cgi?id=85464 https://bugzilla.mozilla.org/show_bug.cgi?id=85464