I think there might be a whole generation of people who are used to printing work on paper, and hence only using one side of the paper - and thinking that is normal. I grew up printing on both sides of the paper (with a printer you had to manually load sheets into one at a time, like a typewriter - very similar method, too!) and writing on both sides.
Back in the glory days when "people knew how to deal with witchcraft" as a picture posted on another thread describes them, people would write on both sides, and write several times on the same side - writing upside-down and rotated through 90 degrees, too!
When I write in an Oxford book or similar, though, I actually only write on one side (the right of the pad) and save the other side for edits, notes, replacements etc. etc. So, I guess I do use both sides, just not as they might think . . .