Liquidmetal is more durable and cosmetically pleasing than a molded plastic. It can be molded into complex contoured geometries like a plastic, and it cannot be dented. That is a feature of being an amorphous metal. Liquidmetal is also very hard, which is desirable for scratch resistance. It is a non-magnetic alloy, making it suitable for use in an MRI environment.
There is also a big advantage to molding housings that contain electronics and optical components. These housings would be very expensive to machine out of a block of raw material. Liquidmetal can mold all the features in one step with the precision to properly align to mating components. Liquidmetal can also be over-molded with plastic and Silicon for applications that have such requirements.