Those 'basic precautions' will not be cheap and would probably require the liquidation of some of their bitcoins since they probably aren't anything like as wealthy in non-bitcoin terms. Liquidating their bitcoins would damage their psuedonymity, which is something that they are clearly not keen to do.

The other thing is that most of those centa-millionaires are not keeping their holdings entirely in cash that can be moved quickly in large quantities psuedonymously requiring only a small piece of information likely to be held by Satoshi.

Certainly, securing multi-millionaires is not an insoluable problem (although it fails sometimes), but I think that Satoshi is likely to be in a situation that make the consequences of being unmasked particularly dangerous and the difficulty of measures to keep safe particularly onerous.

Or they considered it, and didn't care, because if they get it right, they'll always be the "guy who unmasked Satoshi".