I never brush my teeth, but most are white. why is this?

Need to see Dentist: Never brushing your teeth can lead to many unwanted dental probelms and can cause medical problems.As well. I would not hesitate seeing a dentist as soon as you can for you future health!

Poor oral hygiene: I would worry more about the ones that are not white and what might be in progress regarding cavities and periodontal (gum) disease that you cannot see nor be aware of until it's very serrious. When was your last dental checkup? I would also start brushing and flossing regularly. Over the years I have seen many patient who do (or in your case don't do) what is necessary until it's too late!

Anomaly: Most people who don't brush have stained teeth, as well as cavities and periodontal disease. I hope you have neither.