Re: Why not save the planet at the same time?
The migration is constant: from table-based layout to CSS; from XML for data to JSON; … But human readable markup has advantages for longevity both of the documents and the technology.
In terms of energy use you're making false assumptions and equivalents. It is the web's open and reliable technologies that have made so successful and universal – really it touches billions of people. Yes, there is a lot of electricity used to power phones and networks but this is still tiny in comparison with industry.
If I could change one thing in the world today to reduce energy use, it would be to make online shopping more expensive because it is the physical infrastructure behind all those individual deliveries that really uses resources.