FTP, or even SFTP, is really slow. FTP isn't even standard, and every server does it differently (SFTP is actually SSH, which is standard). That's why in many FTP clients SFTP is much more reliable. In the FTP realm Sublime needs better integration with existing FTP clients. I use YummyFTP and it cooperates with editors very well, but only with TextMate and other editors. For example when I open a file Yummy knows when the file is open. If I try to re-open it warns me and gives me a dialog with options. Once I close that file it knows and doesn't bother me when I try to open it again. Since I switched to Sublime Yummy doesn't know when the file gets closed and always warns me.
So I don't think FTP support needs to be built in because he would have to implement his own "engine", which is more trouble than it's worth. With Git Sublime could use command line options (I think there is a plugin interface). The point is there is an existing framework to plug-into with Git. Dreamweaver has built in FTP support and I don't trust it. It's been around for years. I have more faith in my dedicated clients.
For now I use a program called Gitbox, which works quite well.