That is where the additional tips go- the cash handouts. If you use a lot of room service, you tip them more. The thing to do for a 7 day cruise is: take 2-4 50's depending on your preference, and pay the waiter and the cabin steward one or two of those (cabin steward no more than 50, and one of those other 50's for a bartender if you party heavily on the cruise, and the waiter gets 50 no matter what, and perhaps more if you have 4 or more traveling with you or you get excellent service).
Then you bring 100 1's. Those are key! You can tip the porters, room service guys, haggle with local merchants better, pay for cabs, etc. I brought 100 and got another 50 1's from the purser. Should have brought 200 and paid for all souvenirs, etc with 1's!