Why do some cats never purr?

I have a 2 yr old neutered male cat that I recently adopted. I realized that I have never heard him purr.

I'd have to say it's because humans aren't the only beings with personalities. As a matter of fact, all living beings have personalities, and some cats probably just don't purr, like how some people just don't eat spicy food, or some dogs just refuse to be domesticated. I don't know if this is the real reason, or the only reason, but it's just a thought.