Why not all fungi can be called parasitic?

Fungi may not be parasites, but symbionts. Example: mushrooms and plants. A close symbiotic interaction exists not only in lichens, where the plant cell is represented by algae, but also between large trees and all your favorite edible (and inedible) mushrooms. The mycelium braids the roots of plants, from which the mushrooms receive organic substances synthesized by plants, and they themselves produce antibiotics and vitamins. It has been noticed that trees in the mushroom forest do not get sick.