You're right, the common packs are missing from the store. Interesting.
For Andy:
There must be a fixed number of commons you can get?
Some sort of reward would still be nice... maybe you can offer a card, but delete another common? So you're still getting cards at the price of losing cards you don't use... not sure that makes sense.
From someone on the plantsvszombies wiki - http://plantsvszombies.wikia.com/wiki/Thread:587026
"You can only earn a max of 4 of each Basic teammate from generic rewards, so that's why. Congratulations, you've earned every Basic teammate! You'll also notice Basic Packs have disappeared from the store for this reason."
