John McEnroe has always had a huge ego, and has always both loved and sought out the spotlight.
Ergo, that he is doing this primarily to keep his name in the headlines is extremely plausible.
He was a great tennis player. Presently, he is a media wh*re who loves nothing more than a TV camera. Commentating on matches wasn't enough for him - so he went and got his own 'game show' ('The Chair'). That, naturally, didn't last long. Needing even more attention and spotlight, he went and got himself a 'talk show'. Naturally, that didn't last very long, either. His desperate need to be in the spotlight was becoming comical. This doubles thing is just another in the long line of things he does to gain attention and satisfy his massive ego.
Connors' ego matches that of McEnroe, but at least Connors was able to pull himself out of the spotlight. There were several years where Connors lived in relative anonymity; where we heard nothing at all about Connors. McEnroe, I'm afraid, will never be able to accomplish this.
When McEnroe was in his prime as a player, he would relentlessly criticize the phoniness and pretense of all things superficial and 'Hollywood' - and now, he has become the very epitome of that which he always claimed to despise.