Oil change light

What is your question?

I have owned my challenger for nearly 5 years and have put over 38,000 miles on it. I have always changed my own oil. This is my question, the oil change interval has never flashed or chimed during the whole time I have owned the car and I never reset it. Is it possible that something has been shut off in the computer say maybe the previous owner used a tuner etc? I thought it was a duty cycle system in the car. I always change the oil according to my manual 6 month or 6,000 miles. I am more curious than anything as why this function that it originally came from the manufacturer with never works. Thanks