Exactly. It'll be an unsustainable system if there were 100 million users, yet were the market cap <$1 billion. 

This seems like a selfish move by Steemit Inc. to retain holdings, which is in direct contradiction to their stated goals of decentralizing their stake. That was early 2017, absolutely no steps have been taken since. That said, this could be useful to third party developers with a sweeping marketing plan. Even so, the concern is no one can compete with Steemit Inc in the subsidy market, due to their overwhelming RC budget.

If steem goes to $1000 someday, will we get more decimal places? Or will the smallest unit of measurement still be 0.001 and be worth $1?

You're so right, they're trying to fix value related problems with code, an attempt making steem immune-to-the-world-market could be viewed as 'sailing in rocky waters'

>the 'logic' that "there isn't enough STEEM to create millions of accounts for onboarding".

Total agreement, @smooth. I Noticed the same thing after a few seconds looking at account creation faucets and I am glad to see RC taking over, making something like 5.1 Million accounts annually with your calculations. 

We might have to UP those numbers again, just calculated that with 14K accounts per day will take 196 years to get to 1 billion accounts.