Satoshi said the coins he had mined is like a donation to everyone. I can only think he completely forget all those coins and didn't even copy paste the privatekeys of it. Think of it like the supply has been reduced and this is why its impossible for somebody to prove he is the real satoshi. But then its easy to claim. If you have something to promote to the public, you can always organize a conference and have someone to claim he is satoshi to get more audience.