Why do landlords do this?

Why do landlords try to charge tenants for the sum of increases (if any) in operating expenses, plus increases (if any) in insurance costs, plus increases (if any) in utility costs, instead of charging them for increases (if any) in the sum of operating expenses, insurance costs and utility costs? It’s so obviously unfair that landlords ought to be embarrassed even to try. I’ve even seen landlords try this approach and include in operating expenses amortization of capital expenditures which reduce utility costs. Don’t they see the absurdity of that?