You really don't know that. People like to say "I'm just going to tip who wait on me, I'm not helping those I don't see!" but, just like in a restaurant on land, you have no idea what happens to that tip money. Does the person you're giving it to share it with other individuals? Do they put part of it in a "pot" for employee parties?
A seven day cruise w/Royal's tips ($18.50pp/pd currently, right?) would be $129.50pp. Assume two people and you're at $260. That's the "automatic gratuity".
But you like to give cash, so you remove the auto grats, and give $50 to your cabin attendant, $50 to your waiter, and $40 to your assistant waiter ($140).
Then $5 for each breakfast and lunch (another $70), then $1/drink (say $5 per day, so another $35). $245. You're still out about the same amount of money, but you're "sticking it to Royal", because your money isn't "subsidizing" other's pay. Which you really have no idea about.