The point of a bonus is to motivate worker to give their best. But if they are already doing that (say, they are making a video game and it is their passion),

The point of a bonus is to motivate worker to give their best. But if they are already doing that (say, they are making a video game and it is their passion), work extra hours, and on top of that get their bonus cut coz of nothing they can reasonably affect, that just kills morale