Telnet is still quite common in the embedded world. Existing tool boxes have implementations, busybox has a telnet client and daemon built-in, etc... It's easy. If the box never goes beyond a development rack it's safe. And if it's what you've been doing for 15 years there's not a lot of value in change.

Nonsense. People stick with telnet because of ignorance. That is why you remove telnetd, and force them to update. There is no difficulty in switching, and thus no valid reason not to switch.