Some do... in the form of scaling bonuses based on peer review, overtime used by salaried positions, and overall contribution to the company. Essentially a pool

Some do... in the form of scaling bonuses based on peer review, overtime used by salaried positions, and overall contribution to the company. Essentially a pool of money is set aside based on how well the company performed for that quarter. That's your "upper limit" just like there are 365 days in a year for vacations.