Primarily we use synthetic dye because they're cheap to make. Secondly unlike natural dyes these synthetic ones are long lasting and more vibrant in colour. Natural dyes again are not as vibrant or last as long synthetic, but most are to be exposed to and are biodegradable.

 

This raises the question, Why don't we just switch to natural dyes? There a re many reasons why we can't just switch. One being that the manufacturing of synthetic dyes are more cost efficient. if we were to shift to natural dyes it would take time and leave thousands without jobs until the switch is finalized. In countries like China, Bangladesh and India this would be economically devastating. Secondly natural dyes are harder to source, being made of trees, flowers and insects. natural dyes still however require the use of heavy metals in order to have the dye stay on fabric for longer.