Taken from the first link I posted in response to chunky
Quote:
"Clicking does things slowly and thus is less effective than someone who uses keybinds. Clicking forces you to watch your action bars and hinders you from watching what is going on around "
Basically in the end its easier to play the game when you know how to attack and kill something without looking at your spell bar. It's pure memorization and unique from player to player.
If you are attacking something and constantly looking at your action bar and clicking your spells you are handicaping youself. Make your life easier with keybinding, its essential for success.
The reason why people are good is from keybinding. You can go back to other games like Starcraft where the good players were the ones who mastered the hot keys and knew when and how to use their spells. The same can be for WoW, just know that in the end your bindings will only be effective if you are comfortable with them.