That is one thing that bugged me about the game. Everyone goes for what ever is first in the list. The cactus is the "first" healing plant. There's a particular man and woman who are first and get all the attention. It'd be nice if people interacted with random people.
If the developers want to make it more intricate, they grow a relationship with people they see most. As children grow up together, they gain friendship with each other, and from then on they tend to interact with those same people more so than others.