I don't know if they removed it from Vista.
But seriously, do you know anybody using Vista, who knows that you can use telnet for things other than the default term (e.g. "telnet mailserver.foo.com 25" to talk to SMTP/sendmail)? I don't know anybody that savvy, who is running Vista... just (l)users with Vista Home Edition because they had no choice.
They wouldn't know to do it, but when instructed very carefully even monkeys can type what they are told.