In the UK, at 8 hours of operation per day, that 120Hz refresh rate boost would only result in about £30 per year.
But that ecological footprint multiplied by millions of people? Well, that might truly suck. Especially when we add up all the other "quality of life" things we enjoy with modern desktop PCs.
(I don't know how to make these calculations, and maybe this is something you would excel at @baldpolnareffart?)