I wish terminal emulators still supported zmodem natively like some of the better emulators many years ago. It's not too difficult to configure iTerm2 to invoke rz when detecting the escape sequence[1], but it's still too much friction. sz/rz is something I would be using everyday, but I prefer sticking to Terminal.app on macOS--I prefer zero-config environments because of all the various systems, local and remote, I interact with on a daily basis.

scp and sftp are great, but the nice thing about in-band file transfers is that your shell session already has the current context for simplifying the transfer. For example, you often want to send to or receive from the current working directory, or something nearby, and interactive file globbing is just a single tab key away, without having to switch sessions, login all over again, copy paths, etc.

[1] I don't miss automatic printing without confirmation, though. The prank of `cat /vmlinuz | write user` wasn't that funny when the service desk hands you an entire ream of garbage along with a reprimand.

Gnu screen supports zmodem send and receive. I use it frequently to get files into old retro computers I’m playing with.

I’ve used it in datacenters where I’m ssh’d through three intermediate hosts, or when I’m inception-ing down into containers and vm’s

Tweeted about zmodem just last night! https://twitter.com/ryancnelson/status/1306444057602711553