Lattices in Blender are part of the modifier stack and, therefore, require connecting. I think there is an addon that does it automatically, but going through the motions is a good way to learn. one of those “Learn the rules to break them” situations.
One of those modifiers is called the Skin Modifier. it’s a way of taking all on the edges of your model and forming a cage around them, at the same time turning off the underlying structure, so it’s good for cages, fences and all sorts of structures like that.