In the beginning there was just "GAS". Eventually, they added LEAD to the gas to improve engine performance. And they charged more for the gas with the lead.
Later they started making "NO LEAD GAS" again. For some time they sold "LEADED" and "UN-LEADED gas" They again raised the price on the UNLEADED, apparently for REMOVING the LEAD from the gas.
Now, for many, many years they have sold nothing but UN-leaded gas. Since there is no longer any choice to be made, WTF do they not just call it "GAS"?