It's about Steem Power and business habits - with time, some of the older users kept getting consistently high payouts. Whales notice such users and upvote their content. Why? The reason is that whales get better income from upvoting (curating) articles with higher income.

There are very few whales, which upvote minnow articles - and they have my gratitude, for not being selfless.

There's a problem with the Steemit curation and reward system, and have already offered a simple solution here. Developers haven't cared so far.