Board Thread:Tales from the Tardis/@comment-188432-20131126205522/@comment-1166667-20131127030435

Or he (like us) considers the War Doctor an asterisk in his life. He may finally acknowledge that the War Doctor was just as much a Doctor as the rest, or perhaps him now the War Doctor is "THE Doctor", but for a man who sees his past and future selves so often, it would be dangerous to think "I'm #13" if he chances running into an earlier version.

Gallifrey's survival needs to remain a secret. And he can't tell people he knows, what with his time traveling, or he may risk the information somehow finding its way back to him, etc.