Perhaps the person (or persons) is concerned that bitcoin will become even more successful and will threaten powerful institutions like major world governments. I wouldn't want to be Julian Assange right now, and that is a perfectly sensible reason for the inventor of bitcoin to wish to remain anonymous.
A different reason might be a fear that if a single inventor were known that bitcoin would become vulnerable to "change it this way because the founder says so" attacks, weakening the decentralized, P2P nature of the currency. (This is a less plausible reason, but still valid.)
A different reason might be a fear that if a single inventor were known that bitcoin would become vulnerable to "change it this way because the founder says so" attacks, weakening the decentralized, P2P nature of the currency. (This is a less plausible reason, but still valid.)