The reason is that we do not have the full postal codes for Brazil.
Postal Code restrictions:
For Canada we have only the first letters of the full postal codes (for copyright reasons)
For Ireland we have only the first letters of the full postal codes (for copyright reasons)
For Malta we have only the first letters of the full postal codes (for copyright reasons)
The Argentina data file contains 4-digit postal codes which were replaced with a new system in 1999.
For Brazil only major postal codes are available (only the codes ending with -000 and the major code per municipality).