Some of them are selling as they live from that money. I know they have no altruism in their bodies and the majority have been taking for too long.
The good thing is that they cannot grow as fast as the other 45000 active accounts so they are not gaining from the reward pool which they used to have control over. While they still have the majority of power that is changing fast as all of the accounts below them keep growing and earning sp.
Them relinquishing will be good in the long run as the rewards get spread between a lot more people and a much more active community. While I have seen a couple of whales that use the site and interact with people, the majority just seem to sell their votes and sell steem.
Posted using Partiko Android
I posted below.
The SP breakdown is 53% to 47% (roughly) for the Whales/non-whale accounts.
The reward payout is 75% to 25% author to curator.
Even if the Whales wanted, there is a point where they cannot post enough content to monopolize the reward pool where nothing is given out.
As you said, most Whales are passive investors leasing their SP out. Plus, they tend not to be buyers of STEEM since they have so much. The last price drop saw a lot of smaller accounts adding to their positions.