Why is FTP all of a sudden an important interop protocol when we have HTTP, HTTPS, rsync, scp, etc? Why is the browser responsible for maintaining this legacy FTP support when there are command-line utilities and dedicated GUI clients for it?
This whole ordeal kind of reminds me of IE8. Whether good or bad, companies stuck to what they knew and what tools they used to carry out their day-to-day. I can easily see updates being avoided to keep FTP functionality at the expense of newer security issues being patched.
I don't really understand the argument that if everyone else drops support that Firefox should too. Firefox could champion themselves as continuing to support various protocols and live the principles they set out for themselves.