"Was" is the key here. FTP has been obsolete for 20 years.

Widely used? By whom? Devs who don't understand rsync or scp? Give me a practical scenario where a box is running FTP but not SSH.

Edit: then account for the fact that this rare breed of content uploader doesn't use an FTP client... there's absolutely no reason to have FTP client code in a browser. It's an attack surface that is utterly unnecessary.