Apple still includes uucp for some unknown reason.
The saving disk space argument makes no sense because telnet was one of the smaller binaries in /usr/bin.
Telnet continues to be widely used for select use cases and being told we're naughty by not including it feels punitive and just adds extra steps. What are you supposed to do, trash a $1m piece of industrial equipment because Apple wants to remind you Telnet is insecure?
New devices are still being released with Telnet where SSH is impractical or unnecessary.