Popular directors aren't popular because of happenstance or luck. Popular directors are popular because they create great art and produce great results. Speilberg, Scorcese, and Tarantino are names people recognize and that is because of their work.
A great director commands respect and their movies command attention. Directors often remain in the shadows until they create their first masterpiece and it doesn't take long after that before many become household names. Not because of who they are but because of their talent.
There is more to directing than yelling "action" on the set or helping actors stick to their lines. It is a talent, an ability to bring out the best in everyone and a vision few have. And it is that vision when realized that we never forget.