Currently it is not avaliabe in all iTunes Store.
In Australia (which the feature is unavaliable), they only recently began to rollout the new iTunes cards (they have an iTunes logo as the card face + difference colours for different credit values).
From my understanding, they are preparing this feature for the Australian store, but aren't quite ready yet. Once Apple is certain that a majority of all iTunes cards being bought are the new type - the feature is sure to be released.
Key features of the new iTunes cards:
- New card face (hologram iTunes logo)
- New card base (solid cardboard - no longer flimsy)
- The code label is peelable! No more excessive sticky annoying material!
- A square that surrounds the code (used in this camera-detection feature)
As Apple mentions here on 2nd line - Not all country support the feature, but I believe it is coming soon
Hope that help! Have a lovely day!