Its time to go out on top as Jennifer said in her statements. Hudson is a product of American idol show, spokesperson, an actress and Oscar-winner. She says "Everything has its time. I think it should just allow itself to go out on top... and gracefully". So for him it seems that it is better to end while on the top of its rating. It also said that idol changed the face of television, and she is proud to have come on the show.
The rating of Idol is still declining, despite the facts that the set of panel changed. In fact, reality shows such as x-factor and the voice have got the attention of the audience. The simplicity of the show is highly appreciated by the hug audience that's why its rating is going up which is in contrast to the rating of American singing competition.
Many artists become successful because of American Idol including Hudson, Kelly Clarkson and Carrie Underwood.