Think about the last time you were in a treehouse and you had the world for the taking. All those possibilities of far off destinations in your head, or perhaps, the natural scenery surrounding you was all you required to be totally satisfied with your place in life.
Go back to your childhood, and your own story. Dig a bit deeper. Your tree fort was handmade especially for you and your siblings, or it was inherited from the previous generation or homeowner.
Today, when I drive through the countryside I see a variety of structures in sizes and shapes from simple purchased ones to apartment-like complexes expanding across a couple trees.
As for kids, the treehouse fort/hideout/ is an ideal place for discovery as well as downtime.