One has to consider why would he wish to remain anonymous?

One theory is that Satoshi is a number of people, a group.

If so, why pretend to be one person? A group could still be anonymous - eg "Anonymous" "Lulzsec" etc.

Why would an individual not wish to be associated with the creation of bitcoin?

It seems to me 2 likely explanations

1) they didn't wish bitcoin to be seen in the context of their previous writing. I've not read this Discipline book, but if it advocated a political line and the author of it were the creator of bitcoin, it might cast bitcoin in a political light. Eg if it predicts that a crypto currency could topple the US government, then bitcoin would be seen in light of that - ie an attempt to do that, which might turn many (but no means all) against it.

2) they intend to profit from bitcoin. Whoever invented bitcoin stands to make a lot of money as the currency appreciates (as they'd have got the first bit coins very cheaply). The very limited supply of bitcoins makes vast currency appreciation a certainty if they catch on (as appears to be happening). The creator might not wish people to see quite how well he's doing from it. Personally I don't see why the creator of something successful (eg Steve Jobs, Bill Gates, Larry Page, etc) should not make a fortune from it, but many people might use the growing wealth of the creator of the system as a criticism of it.