The reason for this is not very complicated--it is because it is beneficial to organizations to be seen as environmentally friendly.
In today's world, being "green" is relatively popular. While not everyone believes in global warming, being green on issues like saving energy and recycling is coming to be widely accepted as normal. School children learn about being green in their lessons and even many small cities have recycling programs.
Because being green is popular with the people, it makes good sense for businesses and other organizations to appear green. It projects a good, responsible image that is more likely to make people think well of the organization.