Why some people hardly blink their eyes at all, but have no dry eyes from it?

Blink rate. Blink rate varies significantly depending on age and quality of the tear film. With younger age and healthier eyes, the blink rate is much less.
Variable tear film. Blinking is a means to insure surface lubrication by the tear film. People vary in the frequency of their blinking and tear distribution. Often dry eye patients blink more often than average in order to keep a comfortable feeling to the eye area.