It has a tubular cage like that because space frames are about the easiest way to build the primary structure for a one-off or low production vehicle. It's not

It has a tubular cage like that because space frames are about the easiest way to build the primary structure for a one-off or low production vehicle. It's not a particularly safe way to build a car for passengers without helmets. There's no padding on the cage either. Every race series that requires cages also requires helmets and padding.