It seems there are two questions here. 1) Why is there folky stuff on the show? Because it was popular. Popular doesn't automatically mean good or bad. 2) Why is folk best? For me it's what I like best, most of the time. But I still listen to other styles as well.
A story: The ruler Tamurlane was eating one day and had a delicious dish made with aubergines (eggplant in the USA). He declaired the aubergine to be the best of foods. His advisor agreed. The cook overheard, and for the next month, Tamurlane got nothing else to eat but aubergines in one form or another. At last he raged that it was the worst of foods. His advisor agreed. Tamurlane said," but before you said that it was the best of foods. How can you contradict yourself and still speak the truth?" The advisor said, "I serve my ruler, not a vegetable."
But the point in this case is that a steady diet of anything, no matter how great it is, can stop being enjoyable.