The ladder’s house edge on your rank. Just as the casino rakes a slice of every pot, the ladder rakes a slice of every hand you’re EXPECTED to win: your rating is a promise about your winrate, so the better you are than the table, the more of each win is skimmed before it pays rank. Beat the promise and you climb; merely win and you tread water.
Why it exists: without it, a strong player could sit in a weak room and farm rank forever. The rake ties your rank to your EDGE, not your winnings — so a rank actually means "I beat fields this tough." It’s deliberately gentle low on the ladder (climbing feels free) and only bites hard near the top, where the competition is so steep that holding Diamond and Obsidian demands you keep genuinely crushing. That’s why, up high, a break-even stretch slowly slides you back: the rake is the price of the summit. Your bb ± counter is the honest scoreboard underneath it — you can be raked on rank while still stacking profit.