Leno is a commentator, O'Reilly is a commentator, Franken is (was) a "commentator", and the same with Ingraham, Malkin, the bloggers who've gone, etc.
Tiger's not a commentator, he's not a performer, but he IS of military heritage and I'll bet he'd like to show his support, but wonders "What the heck can I offer to these guys by going to LSA Anaconda or Camp Victory?"
He puts it best as is noted above: "I just want to say, Thank you in some way, and this is our way of being able to do that".
Ummm ... His wife?