There are about 350,000 species of plants on the earth. Among them, only about 3,000 species are cultivated for food. The edible plants are less than 1% of all.
Grasses have their own names and characteristics, but before they are known, people regard them merely as weeds. As for weeds, the dictionary defines them as wild plants that grow well though uncared, or as plants that prevent the crops from growing properly.
However, as their hidden efficacy is discovered, weeds are no longer treated with contempt but regarded as precious now. So some people define weeds as plants of which the value has not been found yet.
It must not only be in the world of plants that something is considered unnecessary as its value is not yet known. Even a small insect that was considered to be trivial turns out to play a big role in maintaining the ecosystem, and a person whom no one usually paid attention to achieves a remarkable work in a crucial moment. That is why we need to broaden our horizons to discover the hidden value rather than making a hasty judgment.