While I completely agree with the aspect of making the it retroactive, it wouldn't make much sense to do that anytime soon. SE is trying to get more people to pay and play this game, and aside from the actual gameplay with friends, there's no real initiative to do so. SO, in the aspect of making money, SE wants to throw in some really stellar rewards. If you gave them to people already playing, then there's nothing from stopping you from getting someone in the game to register the code and walk away with all these awesome rewards, you could even ask a stranger to do it. That doesn't increase the player base at all and now the exclusive rewards are all over the place and everyone has it. The fact that you want it is what SE is hoping you'll go into the real world and find someone to throw their money at SE for some more shinies.

I feel you on wanting the rewards, I thought of throwing extra money at SE to make it happen myself, which is also what SE wants. My wife got me to play, i got my best friend to play, and he got his friends to play, ect. so I feel I should get the rewards too, but that's not good business.