Tom Jones was treated very badly by the BBC - the first he heard about being dropped was when he gut a letter to that effect, he took to Facebook to express his disappointment (in a very dignified statement).
I've never really watched The Voice but I went to a TJ concert in Hyde Park with a friend a few years ago, he was brilliant, so giving and appreciative of the audience and seemed to love what he was doing. It was one of the best concerts I've ever been to. He performed for hours.
On the other hand, we paid a lot of money on one occasion to listen to a very grumpy, bad tempered Van Morrison who seemed to think he was doing the audience a favour ...!