To be fair, the expression does contain (edit: ) Euler's Formula, which is basically drawing circles in the complex plane, so people are going to draw circles.

I started thinking about sinusoids this way after seeing stuff like this: https://3.bp.blogspot.com/_6t_ZmJSkbL4/TJLIDoBQMzI/AAAAAAAAC... — if you look down at the complex plane, you will see a circle.