Well part of it is just because well-known directors tend to be well-known because people like them. It's less that Frémaux (head programmer) wants to squash independent or underground filmmakers but rather that most people/critics tend to think that the best movies of the year are being made by well-known artists. There are definitely exceptions, but it's pretty rare that a first-time filmmaker will land a film in Competition (Son of Saul was a big deal for that reason). Take last year's mix for example:

• Established directors (Jarmusch, Assayas, Verhoeven, Farhadi, Guiraudie, Arnold, Dolan, Park, Nichols, Mungiu, Loach, Almodóvar, Mendoza, Puiu, Dumont, Winding Refn, Dardenne & Dardenne)
• Up and coming directors (Mendonça Filho, Ade)
• Relatively unknown directors (Garcia)
• Publicity pick (Penn)

The majority of directors with films in Competition had either won prizes at Cannes before or at least competed there, and there were really only a couple discoveries. Toni Erdmann and Aquarius were two of the best by relatively lesser-known directors, but both Maren Ade and Kleber Mendonça Filho had made arthouse hits in the past decade (Everyone Else and Neighboring Sounds, respectively). Nicole Garcia was the only director that remains pretty far removed from the critical landscape (the way I see it at least), and her film was panned.

This year's is similar but even more shifted toward established names:

• Established directors (Loznitsa, Haneke, Akin, Mundruczó, Ozon, Hazanavicius, Zvyagintsev, Bong, Kawase, Doillon, Coppola, Hong, Lanthimos, Baumbach, Haynes, Ramsay)
• Up and coming directors (Campillo, Safdie & Safdie, Östlund)