Many of you will be too young to know this, but back in the 80s and 90s, pixels weren't even incorrectly "little squares", they were very often "little rectangles". Your display was almost always 4:3, but the resolution of your screen was very often not 4:3, and so if you needed to display squares or perfect circles, you needed to compensate for that.

This is why the Utah teapot looks squashed, compared to its real-life counterpart: https://en.wikipedia.org/wiki/Utah_teapot