In the Australian supermarket system why do management KPIs revolve around not spending money rather than maximizing profits?

The shareholders want maximum profits, but at the store level the emphasis is on minimizing costs even if that means having empty shelves because there is no budget to pay someone to move stock from the storeroom to the shelves.

Every empty shelf is losing money due to the fixed costs of rent and electricity. Plus the customers are less likely to return if they cannot buy the things they expect to see.