What one can or can not afford has zero bearing on the discussion.
Personally, I am very fortunate, and can afford just about anything I desire to have. I do not book cheap rooms. I continue to book (albeit less) despite the rapidly increasing fares. The thousands i spend for a week on the ship should be used to fund the payroll. I have done my part by simply purchasing a fare.
I do not, however, pay an arbitrary pre set amount of cash to any corporation when they make it optional. I (and a rapidly growing number) tip AFTER service is rendered, and in an amount commensurate with the quality of services received.