For one, it’s in the middle of nowhere in Wyoming. It’s pretty much the least populated area in the country. There just aren’t enough people in that area to warrant a huge infrastructure project, and to connect it to the national grid and get power to more people would be a massive undertaking.

Second, it would not reduce the risk of eruption at all, and could increase the likelihood of unpredicted geothermal surface features. Yellowstone is one of the most seismically active areas in the country and much of it is very unpredictable.

Finally, it’s a National Park. We tend to not want to build power plants in National Parks, and it’s actually illegal. There is a law requires NPS to preserve geothermal features in National Parks. To power the entire northwest as you suggest would require a massive facility, and even though geothermal is “green energy” it would still have a huge and damaging footprint in the park. It would alter the landscape and destroy parts of one of the most beautiful and important geological places in the entire world.