Because everything was made of Protodermis for a reason, it is basically the building block of life for Bionicle(no kidding?), and that everything in the matoran universe was made of protodermis meant that they were creations by the Great Beings, I personally liked the idea of this because it is similar to cells or atoms, and they all build up as part of a bigger biological system, and I really think Protodermis should come back to G2, because everything in the Bionicle universe is protodermis, and we should keep it that way! And I don't really want to think the Toa and protectors are made from anything else but protodermis. It's like they are made out of iron without it