One thing to consider is that if the company gave the bonus to all PT hourlies, that'd be a big middle finger to the PT Sups who have been with the company for years but also find themselves making less than the new PT Sup promotions. They don't want to do that, since they can't get staffed with sups as it is. Buying the pt sups an arcade cabinet is way cheaper than actually paying them. At least right now they can say both groups are in the same boat with regard to new hire pay.
Better to kick the can down the road and hope their staffing situation magically turns around before they need to staff new positions due to expansion.