Do you have any idea how many people complained over KH 1.5's announcement that KH2 wasn't part of the package? If you look at the trophy percentages for 1.5 on PS3, you'll find that people hardly bothered with Re:COM, and that a lot of players didn't even watch Days.
Which is why they are packaged with the numbered games in correlation with the plot that takes place within them. Sure not everyone will want to just jump into a game they've never played before, or a two n a half hour cut scene for that matter, if they have the nostalgia of the first KH looking them in the eye. But, when they decide to proceed to the next step story wise it's there.
If they packaged 1, 2, and BBS in one remix and Re:Com, 358, and Re:Coded in another it's not hard to tell which would be the better seller. But by having it the way they are as they stand they are balanced and are organized, so anyone trying to play catch up with the story or going through a refresher has it easy. It's a bit of both practical and convenient really.
