[Benholio]

The reason is simple. The affiliate does the same amount of work regardless of how often you play. As you play more and more, he is making more money from it, so can afford to give you back a bigger percentage.

Say you have 3 players, who generate in rakeback for the affiliate:

a: 3000
b: 300
c: 30

If the affiliate was getting 30% and giving back 25% to each player, he would make, $150, $15, and $1.50 off of the players. Why waste time with player C) for $1.50?

With a sliding scale, it evens these numbers out by raising the amount made from the lowest players and lowering the amount made from highest players.