That’s because the back-end costs of fossil fuels, their so-called “externalities”, total in the trillions, yes, trillions, of dollars. These come in the form of massive environmental damage and massive health care costs driven primarily, though not exclusively, by air pollution created by the burning of fossil fuels.
These costs are NOT included in the dollar and cents price we pay for fossil fuels such as gasoline. They SHOULD be. If these costs were actually calculated into the price of gasoline, oil, coal, etc., fossil fuels would not be “cheap”. Indeed, they would be extremely — and appropriately — expensive!
This is how we, as a global society, have arrived at the MYTH of “cheap” fossil fuels. In fact, fossil fuels are so expensive that we simply CANNOT afford to burn them anymore. Which is why we need a switch to 100 percent renewables as soon as possible!