There is also the fact that the "modern browser" is no longer a browser but a program which runs remote code with local privileges and sometimes with elevated privileges. The main reason they want to deprecate ftp is the same reason they used for other protocols: it is much easier to control 1 protocol (https) instead of 10 (http, ftp, rss, ntp etc.). Especially when they decide which certificate is trusted in their browser (which browser (engine) happens to be the only one used by the majority).
Comments
There is also the fact that the "modern browser" is no longer a browser but a program which runs remote code with local privileges and sometimes with elevated privileges. The main reason they want to deprecate ftp is the same reason they used for other protocols: it is much easier to control 1 protocol (https) instead of 10 (http, ftp, rss, ntp etc.). Especially when they decide which certificate is trusted in their browser (which browser (engine) happens to be the only one used by the majority).