Because his commercial value is worth more than many small countries. No doubt this announcement is part of campaign to attempt damage control advised by Tiger's people, trying to recoup some of his lost value. The problem is (I think) that it is just damaging it more. If he and Elin were to just divorce, it would probably go away faster. Any perception of Tiger as a morally upright role model type of figure is gone, and it isn't coming back. Fortunately Tiger is a phenomenal golfer, and the sooner people can begin to focus on that again, the better for all interested parties. For him to continue be a media presence for any other reason is destructive for anyone with any vested financial interest. He seems to actually want to remain with Elin is that because he really loves her or he thinks it is better for his image I have no idea. If it is the former good for him if it the latter then he is just an ass.