Why do golf balls have dimples?

The dimple patterns on golf balls determine the trajectory and spin rate of the golf ball. The higher the ball goes, the more distance you'll get. That's why golf balls have different dimple patterns based on the type of ball it is. Balls come in 3 different categories(low spin rate, medium and high). The tour level balls have the highest spin rate. With all that being said, there's not much difference in distance between a "distance" ball and a premium(tour level) ball; about 7 yards on average. The difference comes in the spin rate which is helpful for the short game. The covers are softer on the premium balls so they'll stop on the green while the distance ball will roll since the cover is harder.