We need a balanced porfolio of energy sources, including coal, to manage energy supply risk.
We don't want to become over-dependent on coal alone in case there is a coal miner strike or a railroad strike. We'd need nuclear, natural gas, hydro, etc., to be available and online to pickup the load for shuttered coal facilities.
Coal is an obvious choice, simply because we have a 500 year supply.
No other energy source can claim that. Even the largest overburden movers (GEMs) in pit mines are electrically powered. Most coal plants aren't dealing with an on-time delivery, but have a stockpile of coal on site. A lot of locals would have to work together to strike and stop the supply, and they'd have to be across the country. While one mine here or there might have a strike, I don't see all of them doing so, because not all of them mine in the same way: some are underground, others open pit.
Railroad strikes would affect more than just power generation, the railroads are vital for much of what people use on a daily basis.
Natural gas is a great on-demand power source, but it can be interrupted by pipeline breaches. Oil is a relatively minor source of power generation (0.4% in the US), not counting diesel backup generators and other small site units.
(We actually use those to supply living quarters and command center power on wellsites, because of the number of computers involved in drilling an oil well now, from the Rig controls, monitoring systems (video and data), etc. All of that is less tolerant of 'dirty' power than it was in years past.)
Hydro is generally dependable, so long as there is water behind the dam. Some peak load facilities use it, too, where the topography lent itself to being able to pump water to a higher reservoir to dump through the powerhouse into a lower one (Bath County, VA).
Nuclear is good, steady unless overwhelmed by idiots or tsunamis, but the spent fuel disposal problem persists (many spent fuel rods are stored in pools on reactor sites). Reprocessing was essentially shut down in 1977 by presidential decision (Yep, Carter), citing concerns about expense, technical considerations, and the possibility of nuclear material being diverted to unsavory types ("proliferation"). And it was cheaper to process fresh Uranium oxides for reactor fuel.
Wind and photovoltaics (and other solar) have proven to work, weather permitting, but have proven in practice to be more expensive and less reliable than had been hoped by their proponents. They are not generally reliable as a steady source. That said, about 35% of the electricity generated in North Dakota (which generates more than double what we use) is generated by wind. Most of the rest is from coal, with smaller contributions from hydropower and natural gas generation.
