Why do cats purr? Some people think cats do it because they’re happy. Others think cats do it just to annoy people who don’t like cats. Like any question, there’s usually a scientific answer if someone is just willing to take the time to look at it.
Cats purr by using their larynx and diaphragmmuscles, both as they inhale and as they exhale, and that’s about all scientists know about purring. They speculate that cats purr as a way to relieve stress much the same way people laugh, cry, or become social maniacs.
The purr of a cat does represent the exact frequency used to heal bones, so after a cat trips you up, it can heal your broken leg as you lie on the floor helpless for the next few days. Ultimately the answer as to why cats purr is that scientists don’t know, which tells you more about scientists than it does about cats.