A lot of people prefer physical keyboards than virtual ones on cell phones. In order to mimic physical keyboards experience, most cell phones have the vibration feature(i.e., the phone vibrates when people are typing). However, I don't think people like this feature based on my observation. Even when the feature is turned on by default, people tend to turn it off. Why is that? What's the rationale for having the vibration feature, maybe it's helpful for people with disabilities?
Haptic feedback is provided to inform users that an interaction is taking place. To quote this research article about Haptic feedback on Keyboards
Consumers evaluating a standard Android keyboard say they prefer options that employ HD haptic effects compared to the non-haptics and standard haptics alternatives: With HD haptics, a virtual keypad feels more like a real keypad during the typing process.
That said, coming to your question why people turn it off,the issue with Haptic feedback on keyboards is that the feedback is continuous and that would be a distraction to users.
That said,haptic feedback does have its place in accessibility as this feedback mechanism is important to people with visual disabilities to be aware of the interaction between them and the device. To quote this article
Haptic feedback tablets are opening new doors for students with visual impairments, especially in math class. Haptic feedback provides a small vibration when the screen is touched allowing you to feel the screen. Haptic feedback is available on some Android phones and tablets. Some schools have begun to use tablets that vibrate went touched to allow visually impaired students to feel shapes and graphs.
One personal reason I don't like haptic feedback is that it is noisy. Watch someone type out a message/text with haptic feedback sometime - the noise catches your attention even if you're not the only one typing.
Another personal reason is because it eats up my battery time.
I found this article really interesting: http://m.pocketnow.com/2013/07/16/why-i-hate-haptic-feedback
Some users don't like it because it feels redundant. They can see they clicked the button with other UI clues - they don't need to be beaten over the head with it. The comments on the article also bring up an interesting point - so many of phones use a very strong haptic feedback - when perhaps a more gentle vibration would be better.