To me this 2.5" and under size is all about flying anywhere and everywhere. They are tiny, so remain maneuverable in small spaces. And they are super lightweight, so completely harmless. Nobody is going to argue that these are not fun toys, as opposed to despicable and dangerous "drones."
IOW, it's 50 percent about physics and flying dynamics, and 50 percent about public perception. This makes micro BL quads (and their brushed siblings) 105-percent cool!