James Arness actually had a very good reason for why he didn't like doing interviews
Arness was a notoriously reserved person.
Fame can sometimes feel like a double-edged sword. Sure you get to do what you love and perform, and you get the fame and adoration that comes with the profession. However, this also means that you're the perfect target for the press. Hungry journalists are constantly looking for stars to write a column on, begging for personal details ranging anywhere from what they ate for breakfast to their greatest embarrassment.
Like any leading Western man, James Arness was just as known for his reserved nature as he was for his phenomenal acting as Marshal Matt Dillon of Gunsmoke. Despite his extra-long tenure on the series, Arness had gained a reputation among the press for being a private person, declining many interviews.
Ironically enough, Arness actually revealed the reason for his distaste of interviews during one with Knight Ridder Newspaper. While Arness acknowledged that there was a certain part of him that simply didn't like interviews, he also explained that in many discussing his character, he simply had nothing to say.
The actor said, "When you play the same character in the same show more than six hundred times, you literally run out of things to say." While Arness enjoyed playing the character of Matt Dillon, there were obviously times when it began to feel a bit repetitive after a while.
However, in the same interview, Arness explained that at the beginning of the series, he didn't necessarily see playing Marshal Matt Dillon as much of a challenge because of the sheer talent of the Gunsmoke creators and writers.
He said, "The character was so strongly written that you could almost bumble your way through it. I just tried to stay on my feet and not bump into the furniture." Obviously, Arness did much more than that, as his portrayal could be argued as the factor that steered Gunsmoke to its stardom as a television series.
Arness described the show's trajectory to fame as much more abrupt than anyone realized. He said, "Suddenly we went from relative obscurity into total nationwide [fame]. It hit us so big, so fast."