valid Only allow connections when the remote user can pro-
vide valid authentication information to identify the
remote user. The login(1) command will provide any
additional user verification needed if the remote
user is not allowed automatic access to the specified
account.
So vista and juniper don't implement SRA and the connection is not allowed.
The default NetBSD telnetd configuration is more secure since passwords are
not sent in plaintext over the network. This is why valid is the default.
If you want to send your passwords in plaintext, feel free to change it for
your system, but I don't think that the change is appropriate for everyone.