Why do golf balls have dimples?

The answer to this is simple: Golfers want to shoot as low of a score as they possibly can. 

Golf balls were smooth way back in the early days of golf. But over time, golfers realized that their ball would stay in the air longer and go farther when it became scuffed up after some use. The scuffs on the ball caused by trees and other hazards reduced the resistance their balls faced when flying through the air. Over time, golfers started to notice this phenomenon and started experimenting with different golf ball designs.

We will always want to play better. That is what makes a golfer a golfer. So since the early days of golf, we have experimented with equipment to shave as many strokes off of our game as possible. Golf ball manufacturers are still working on ways to improve the modern ball, and always will until limits are set on the performance of the ball. 

That’s why golf balls have dimples - We want to go low.