Coal producing states have been locked into an economic argument where the economy is run by coal and therefore controls the politics. If we were able to produce a legal crop for legal usages this would lessen the grip of coal in the politics of those states.
This would allow for more diversity in political candidates and the economic interests of the populace of parts of PA, KY, WV, etc. would not be dominated by one industry.
Medical marijuana is approved in 20 states and the District of Columbia. So the demand is there plus a few states that have passed non-medical uses.
This would reduce the power of the coal industry in these states and allow for different political outcomes.