Because chemical fiber is synthetic with petroleum and other raw materials
The price of pure cotton fabric is relatively high, and the working class and farmers who make up the majority of the population can't afford to wear it.
The production of chemical fiber will produce a lot of pollutants, consume a lot of energy and water, and the degradation rate of chemical fiber waste in the natural environment is very slow,so it is generally believed that wearing cotton fabric is more environmentally friendly than using chemical fiber