The maxim "The Customer is always right" comes from management and or ownership of a customer/retail business whose purpose was to promote the feeling in current and potential customers, that their needs were paramount to all other concerns, as a way for the business to procure and retain more customers, so that the business thrives and profit is made.
Employees feelings and work environment were purposefully ignored as being far less important than the income generated from customers who experience complete satisfaction in the transaction of money for goods and services, and can depend on their being equitable recompense should any issue or problem occur, to their ultimate benefit.
This was never an employee concerned protocol, only a customer and profit driven protocol, which businesses employed, and still sometimes employ.