The longer they wait to buy in and become "insta whales" the more they are going to drive the price of Steem up. If someone tries to pump a billion dollars into Steem, it's going to increase the market cap way way higher than a billion dollars. Supply and demand. Plus, they still wouldn't have the most Steem. Millionaire whales that HODL and refuse to sell would become "billionaires" over night. Also, it wouldn't be hard to make a bot that simply canceled out another whale's downvote if you had the SP to back it up.
The whales on this site have honestly already been selected. This is a problem that EOS is trying to rectify by having a year long ICO period.