2. My point for 2 is that not all traffic needs to be encrypted. If there's no confidential or private data, why waste the CPU cycles?
3. I disagree. Having telnet available by default does not open any new attack vectors.
4. Telnet may not be designed for it, but that's how it's widely used. SMTP and port troubleshooting have been done with telnet for years, and quite successfully. I think there needs to be a balance between availability and protecting the user, and on a server OS, that line should probably lean towards availability since an advanced user is assumed. By your reasoning, the 'del' command shouldn't be available by default because an unassuming user might delete an important file.