Say you need to use an AoE to break a cap. If you click, you need to move your mouse from where it is to the bottom of your screen, click, then move your mouse to middle of your screen to drop the AoE. If you key bind, all you do is hit the bottom and move your mouse to the spot, and drop. As a key binder your mouse will usually already be close to this spot. It may not seem like a lot of time, let's say a second difference, but it could be the difference between a win and a lose.
If you learn to keybing, don't have to key bind everything, you will become a quicker responding player. It will make you better. And if you keyboard turn stop that immediately, just remove turn left and turn right from your keyboard make them strafe left and strafe right. It opens up 2 more spots for other key binds.