Why are mosses low-growing plants, while ferns are mostly large in size?

Mosses and ferns are spore-bearing plants. Mosses are much older than ferns. They already have not only tissues, but also real organs – a stem and leaves. But there are no roots yet. They absorb water with the help of rhizoids, but these are simply cells of the integumentary tissue that cannot keep the plant in the ground. Mosses grow in large groups and cling to each other. Ferns already have true roots that can hold them in the soil. That is why ferns are large, and in the Carboniferous period they were even trees.