That free month was not included with the expansions when they first came out. (nor was a free month included with Mist of Pandaria for that matter, to include the collectors edition.) It was tack on when they decided to package Vanilla (1.0) BC and Wrath as one product. So you are still only getting 30 days free for the initial purchase, not an additional 30 days per expansion.

However, you did get 3 free month if you agreed to play and pay for the game for 12month and then bought the CE version of D3. But that was because agreeing to play and pay for a year you were rewarded with a free copy of regular version of Diablo 3. Which if you ask me, FFXIV even with the trouble logging on to servers with low ping, is a better product than D3. They will resolve the FFXIV server log on issues, they will not resolve the D3 end game issues (D3 has been out long enough for them to fix it).