Do people really print a lot of email?

I am surprised at how many people (not just in Microsoft but everywhere) have something at the bottom of their email to the effect of “please save paper by not printing this email”.  Is email printing and filing really so prevalent an issue that people are compelled to campaign for its eradication?  At the moment I have 23,146 emails in my mailbox. If we assume each would run to an average of 5 pages when printed and an average paper width of 0.1mm and not allowing for compression, that would print out to a pile of paper 11.5m high. That is approximately 2.6 London double decker buses on top of each other. But I don’t plan to actually print my email to find out.

Doug