It’s the school’s fault. They say so. But not here: most information designers create junk charts when using areas. In 7th grade kids learn how it is right and wrong. It makes them competent with media.
Lambacher Schweizer: Mathematik für Gymnasien 7, p. 122. (click for translation)
Teachers have their book with solutions. On page 81 it says:
left: essentially a column chart – one car symbol represents 10,000 cars; reasonable
right: length and height increase by 66%; perception is distorted, because the area is doubled
Now, I wish more competent media to all kids competent with media.