Biofuels from algae is the only efficient and potentially scalable solution in that area for the US, known for quite some.
Yes, solar and wind don’t work everywhere and are not scalable even where they do work to support the entire grid. However, they could be easily scaled way more in the places that they do work.
As for ‘just because you can, why should you?’ There are a host of reasons, ranging from national security to pollution to climate change. All of which seem to warrant renewable energy as a national focus and as such one that deserves subsidies to overcome the resistance of the status quo forces.