If you aim at something (a target, the middle of the green, a basketball goal), you may just hit it.
What's true in marksmanship is true for markets. No archer can hit every target at once; no company can reach every customer. Focus, then, helps you grow. By limiting your core offering or audience, you'll actually attract more business.
You cannot (and you should not) lead everyone. Your goal is not to increase your ranks until you have legions in your care. Your goal is to take those who identify with your story and equip them to reach that destination together.
Leadership focuses. It focuses on the right people doing the right things to get to the right goal.
Aim well.
Thanks to this Seth Godin post for jumpstarting this idea in my head.