Indeed, X liberated us from expecting workstations to only be clients and servers to be some big iron where I go to get service. What X began, lightbulbs (with embedded servers) are now completing.
I am not an authority on designing network protocols by any standard, first using two separate connections for commands and data seems strange enough to begin with (at least to me). But I cannot imagine what possible reason the people who designed the protocol had.
To be clear, I am not certain if I would have done a better job.
Either way, I was very happy when I discovered sftp. :)
FTP always seemed to me to be a design that was never fully implemented. There's a hint that downloads should run in the background and in parallel while you look around the directories, but FTP clients and servers for a very long time were stubbornly single threaded.
One also has the impression that FTP was supposed to be integrated into your shell and avoid the clunky client entirely, but the design wasn't quite there to support it, so we got the worst of both worlds. A funky network protocol that ran into a lot of trouble when firewalls and NAT appeared and a primitive placeholder client that only downloads a single file at a time.
