Why do not even the largest mosses reach more than 80 cm in size?

First, let’s start with the fact that mosses have no root system as such. Secondly, mosses usually grow in conditions that are not very favorable for growth and development. Also, the plant does not have such a tissue that could transfer nutrients from one part to another. The moss root is only needed to stay on the surface and grow. In other plants, the root has the function of absorbing nutrients from the soil. Mosses absorb these substances by the entire surface, and not by the root. That is why they do not grow to large sizes.