Why Sora didn't go around sealing keyholes in KH II? Did him locking the one in Hollow Bastion effectively lock all other keyholes? Were the heartless only organized enough to be going for the hearts of worlds when lead by Ansem SOD? Or is Sora too preoccupied with opening paths to new worlds he just doesn't care about making it so the heartless can't steal that world's heart?

 

I just have always wondered that. Am I the only one?

I thought that too. It was a little confusing for me actually. The heartless side with whoever is strongest at the moment, right? When I replay the game I will pay more attention 

Though also even if the hearts of the worlds weren't in danger at that time, what stops them from being in danger some time in the future? Locking their keyholes would do just that.Though in KH II it seemed like the Heartless were just causing chaos, manipulated by the organization, lead by Pete and Maleficent, or I think twice by the bad guy of that world.

I always thought he was sealing them while opening new paths for other worlds.

ignorance is a bliss.

Well, he did seal the one in Timless River.