The thing I don't get about UFOs, assuming the alien hypothesis, is why are there so many different kinds of them. Surely aliens would have settled on one, per

The thing I don't get about UFOs, assuming the alien hypothesis, is why are there so many different kinds of them. Surely aliens would have settled on one, perfect, scalable vehicle design after millions of years of refinement? Spherical, probably. Instead, we get saucers, spheres, cigars, triangles...