Coal-fired power plants are disappearing in the U.S. for two reasons.
First, fracking has unleashed enormous quantities of natural gas. This has driven the price power plants pay for gas down dramatically. At the same time natural gas prices have been falling, coal prices have been rising.
This is making natural gas and other alternative energy sources more attractive. For example, the cost of solar and wind power has fallen steadily over the past decade, making those sources more competitive.
Second, it costs more to operate a coal-fired plant than one that runs on natural gas. Coal has to be crushed and washed, and the residue cleared from power plant boilers. These are steps that are not needed for natural gas and renewable fuels.