Why are there no animals with three legs?

If "Why?" is the first question in science, "Why not?" must be a close second. Sometimes it
If "Why?" is the first question in science, "Why not?" must be a close second. Sometimes it's worth thinking about why something does not exist.

Why don't animals naturally have three legs?

Project: That there will be a robotic leg for animals the has 3 or

Plants and Animals – Vigyanam

Deadly appetite: 10 animals we are eating into extinction

legs Archives - Futurity

Why is there no “three-legged creature”? - GIGAZINE

क्या हैं 3 पैरों वाले जानवर का गुत्थी! - Why Are There No Animals With Three Legs ! – Vigyanam

Screaming hairy armadillo Smithsonian's National Zoo and Conservation Biology Institute

Brown-Throated Three-Toed Sloth

Evolution News - Page 61 of 68 - SciTechDaily