There are some actors out there who have become better known as directors, especially in television. I think of Penny Marshall, who played Laverne on "Laverne and Shirley" but didn't do much acting after that show ended. Former actor Michael Lembeck had a decent career playing small roles in sitcoms, but turned out to be a much more successful television director. I think some people with the goal of becoming directors will start out as actors just to get the experience. When they finally get a chance to direct, they'll understand how actors work and how to motivate them.