This assumption is at least partly wrong based on what Hal Finney says in this thread:
https://bitcointalk.org/index.php?topic=155054.msg1643833#msg1643833When Satoshi announced the first release of the software, I grabbed it right away. I think I was the first person besides Satoshi to run bitcoin. I mined block 70-something, and I was the recipient of the first bitcoin transaction, when Satoshi sent ten coins to me as a test.
I assume Satoshi has many coins but I don't begrudge him any of them. He deserves them but I suspect he is not some one whose main motivation was to become rich.
Also my understanding is that the first block is un-spendable. I think I've read that Satoshi did this as he was the only person who could mine this block so it would be unfair if he could spend it but subsequent blocks were up for grabs by anyone who was mining (admittedly in practice probably only Satoshi and maybe Hal and some other very early adopters).