Because oil is the competition. If I can burn oil to generate electricity very cheaply, then I'll do that. I might be willing to pay a little more for renewable

Because oil is the competition. If I can burn oil to generate electricity very cheaply, then I'll do that. I might be willing to pay a little more for renewables, but not a lot more. If oil prices drop, renewables will have to cut their prices too or else lose their customers. The cost of making solar panels probably don't fall that much, so renewable energy companies will lose money. Only very strict regulations could decouple the prices of oil and renewables.