Because he is the one who brought bitcoin to life. And i really think that there would be not much resistance against what he claims to be right. He is simply so very much trusted.
Only his words would be listened to and considered. You've seemingly totally missed the point of the whole anonymous act.
Bitcoin was designed to be protected from the influence of charismatic leaders, even if their name is Gavin Andresen, Barack Obama, or Satoshi Nakamoto. Nearly everyone has to agree on a change, and they have to do it without being forced or pressured into it. By doing a fork in this way, these developers are violating the "original vision" they claim to honour.
Yes, his words. I don't await him coming out publicly showing his face.
But i think you made a good point why he won't say anything. He most probably knows that every agency in the world is interested in his identity. Him speaking now would be way too risky. The NSA or so could find out who he is pretty easy probably. And i'm sure he will avoid that at all costs. Since he doesn't trust banks and probably not the governments too.