Because there main purpose should be to grow the platform which involves spreading rewards to as many new people as possible. If they take more of the reward pool, on top of us fighting the abuse from others, they need to recognize that what they take from the pool is less that is going to a minnow.
They still gain 95k steem year, currently, and gain rep from up votes people give to their canceled out rewards.
I would even agree to one post a week or something so they can get some SBD flowing in their pockets.