Really it's only because Steem is worth less than $100 million. If it was $100 billion (or ~20% of Facbook), your vote would be worth the same as a 6k SP account today, which would be ~.02 SBD.

As far as the current threshold to actually push .001 SBD, I'm not sure. I push close to .05 SBD, so I would guess you would need 1/50th of my acct, or ~270 SP (.79 MV) to push .001 SBD with the current price of Steem.

As a non-investor, influence currently needs to be earned through creation/engagement. However much creation/engagement one seeks to produce is completely up to them. Just like how much one chooses to invest.

Also note that as posts get bigger, your vote pushes more and more. I have an attempted miner account, @boomer, which can push pennies when a post is over $10.