We, in the West, all live in developed capitalist nations. But the one thing we all pretty much agree on is that unfettered capitalism and free markets don't actually work. The problem is that companies have a duty to their shareholders, and no one else. In fact, in most nations, companies that don't put the interests of their shareholders first are legally culpable. So how do you get companies to do stuff in the national or local interest if it isn't in the interests of their profits and hence dividends to shareholders? The answer is we legislate, offer subsidies, and enter into public-private partnerships. And before my Republican colleagues argue that they disagree with what I've said, they have supported clean air policies, clean water policies, introduced cap-and-trade on sulfur dioxide emissions, broken up companies with virtual monopolies, etc. So, as I said, everyone agrees that interference is necessary ... the disagreement between political parties is really over how much!
Coal is a valuable resource not only in terms of energy production, but also in terms of various chemicals and byproducts we need. The steel industry, for example, is dependent on the production of coking coal. Filters used in medical devices, like kidney dialysis machines, are also created using byproducts of the coal industry. Mining of coal also provides us with metals, including many of the rare-earth metals used in the semiconductor industry.
Politicians live in the real world where compromise is the only solution. Sure, we could ban all coal but we'd have to replace coal powerstations with other types. Who is going to pay for that? We could ban coal and then have to worry about unemployment in that sector, and unemployment in other sectors dependent on coal products. Do we import those products from other nations instead of producing them ourselves? We'd like companies to develop cleaner coal, but what's in it for them other than huge costs in R&D that hit their bottom-line?
So, my opinion is simply that many sectors will require subsidies, including the coal industry, if we want them to do things that benefit us rather than their shareholders if those aren't exactly aligned. However, subsidies are, in my belief, the weaker, lazier option by politicians. Rather than actually legislate and create the environment in which companies must operate (which would be seen by many as unwanted government interference) they go for subsidies instead. It basically transfers the burden onto us rather than the shareholders. The rich get richer and we all pay for it rather than create the environment which forces companies to use some of their own profits to become compliant with that new legislation.