First of all, FPGAs are more power efficient than GPUs. GPUs get about 2 Mhash/J, but good FPGAs get about 20. Getting the same work done with less wasted energy (and environment) should be the goal of any sane person. Of course, the initial cost of FPGAs is a problem, and GPUs are better in the short run.
You say this but don't understand the real-world relevance. Bitcoins have most certainly gone up in price due to GPU mining and lack of energy efficiency. The more energy put into the system, the more coins cost to make, the higher the bitcoin price is. If less energy is wasted, more people mine because it is profitable. For now, of course. But the more demand that is created, the more tempted coin hoarders are to sell and waste your effort. Such a self-sustaining system.