Speculators are those who buy and sell "merely for the purpose of sort-term capital gain" without buying or producing what they need. The market price loses the "substantial anchor" there, it becomes turbulent by unreliable information and rumors and extremely unstable. Both consumers and producers are forced to plan consumption, stock goods and adjust inventory according to this market price, therefore they cannot escape this instability. From "The Theory Of Capitalism In The 21st Century" written by the economist.
"January 24 2019
from “Oriori no Kotoba” by Kiyokazu Washida, The Asahi Shimbun"