The whales keep most of their steem in SP. Just go to steemwhales.com you will see there are HUNDREDS OF MILLIONS of dollars in steem power sitting there. Sure, sometimes whales will power down, but they likely won't power down all of their steem power, then they wouldn't be whales anymore. I have both made $$$ here and invested. That's how I've gotten to almost 1,000 Steem.
You are absolutely right, and the System of Steem was designed for people to Keep the Power!
Although It's not the whales who make the Value Of Steem grow,
It's the New Investors that Bring in additional money!
As long as steem has more investors coming in then people Cashing Out the money from steem, It will keep the growth!