Board Thread:Rebirth: Applications/@comment-25152698-20141023012652/@comment-25152698-20141023040750

It's not just to give him an extra boost to sensing, it's to fix his eye sight. Because his kg makes him focus so heavily on his nose, his other senses have naturally deteriorated over time. (For example, bad eye sight in real life = very good sense of sound, which is why deaf people can hear very well.) The Byakugan was given to him by Orochimaru in order to be able to conduct his missions properly. Not being able to see properly would have greatly hindered him.