They still sell Dragon Frontiers pacs around here too. Power Keepers preconstructed decks are also pretty common.
As far as pre-D/P sets go, I still see packs being sold for Power Keepers, Dragon Frontiers, and Crystal Guardians by themselves. They're pretty rare though, since they typically get cleaned out when the store puts them on discount. Most of the packs are packaged by "Excell Marketing," which is apparently unaware of set rotation and continues to re-stock the TCG section of some Target and Wal•Mart stores with older sets, but not very often.
There are a few places that I see packs of Legends Awakened, though they're in remote areas or easily-missed department stores. I know of a Target, for instance, that's in the middle of an industrial area with tiny roads. It's far from any major roads so fewer people know about it than usual. Each time I check there, there's about 2 or 3 Legends Awakened packs left, though now even this place has none.
Set rotation is certainly not a part of the reason, as Legends Awakened packs have been scarce since the beginning of 2009 around here. Now that the Platinum set has come out and people have gotten back into Pokémon, the packs are flying off the shelves faster than ever.