Dynamic Loft is the amount of loft on the clubface at impact when the ball is at its optimal compression. The golfers attack angle, the way the shaft bends, in what way the golfer releases the club head, whether the club face is open or closed to the path of the club, and where on the face the ball hits are all factors taken in calculating dynamic loft.
Making the proper dynamic loft can improve ball trajectory and increase carry distance. Having too much Dynamic loft will cause the ball to reach a trajectory that’s too high causing the ball to lose carry and increase spin.
On the contrary having a dynamic loft too low will cause the ball to have a low trajectory, lose carry distance and increase roll. Both of these examples will cause trouble in distance control due to the fact that you are either delofting or lofting certain clubs, causing distance gaps between clubs to widen making shots with each club either travel the same distance, or distances too far apart hence creating those gaps.
The importance of dynamic loft for golfers is to control distance with each club in their bag. Getting the dynamic loft on each club to be optimal according to your swing will allow you to make distance gaps between clubs equal, making club choice easier when hitting shots on the course.