I think because it provides a visual reference for not just where in the file you are, but how the whole file looks, and lets you say, "I want to go there." Ac

I think because it provides a visual reference for not just where in the file you are, but how the whole file looks, and lets you say, "I want to go there." Actually, I think you could probably make a vim plugin that emulated it's functionality, though probably not with it being readable.