It is required as per CIC
See the official link :
http://www.cic.gc.ca/english/helpcentre/answer.asp?qnum=845&top=15
"Keep this letter. You must show this letter to officials at the port of entry when you arrive in Canada to get your study or work permit."
You're supposed to get this letter in the mailbox of email id you gave in your application.
If you're really looking forward to get it, there's a way out.
The steps are too extensive for me to explain, but you can easily find them anywhere.
1. Register an account with CIC (through GCKEY)
2. Link your application to it.
3. After that, you should be able to see the messages regarding your application.
4. See above (POE Introduction letter) - that's where it is .
Problem solved!