This is about not paying gasoline or diesel excise tax for road maintenance.
Electrical Power generation, regardeless of by coal, natural gas, nuclear, hydro or other sources is not paying that tax.
Like it or not though, electric power generation is a public utility commodity regulated by the state (most of them, anyway).
But I take your point. It is about money, period. To me, the various state departments of transportation are one of the most corrupt parts of government there is. Road contracts, highway maintenance, resurfacing, bridge work, and on down the line - all hotbeds of corruption and kickbacks IMO.
Regardless of all this, I am glad to see that government(states, anyway) is no longer willing subsidize tech that cannot stand on its own two (four) feet and be commercially competitive.