Edit: I think this might have been posted to the wrong thread. I apologise!
Hey, it is totally up to you whether you tip or not! Just know it is just like Uber and other places if you don't tip don't expect the best service. I did DoorDash and Instacart for a short time and I will tell you right now I wouldn't touch an order that didn't have a minimum amount. If the person baited and switched on me I posted that ***** on forums of other delivery people in my area, so the person would effectively not get their food very fast. On cruises, they will make sure that you can't complain about them, but they are not going to go above and beyond for you or anyone in your cabin. My understanding is that they can see who is and isn't prepaying the tipping, or at least some can see the list and they make sure the non-tippers are known by all who your tip is shared with. I have heard it called the crew mafia. If you want extras there just won't be any available, but your neighbors will all get them because they are tipping.
Second, that tip of $18 a day is spread amongst a lot of your service staff. So your room stewards are not the only ones getting it. They are getting a few dollars of it, your waiters are getting a few dollars of it, your bartenders are getting a few dollars of it. The list goes on of service people who get a cut of that $18. Therefore it isn't that much, since I will easily tip $20 for a dinner at a nice restaurant and you will be eating at those restaurants 3 or more times a day. As a non-drinker of alcohol, I am amazed at how much and how drunk cruisers can get and stay throughout their whole cruise. When I was working as a server in restaurants bars and bars I made a lot more per table than $18 in tips. Frankly, as a bartender or server in a bar, I would much rather have you not pre-pay your tips, because the tips start with $1 in the first round, and by round 5 everyone at the table is calling me sweetheart, and throwing 5s and $10 and even more at me. Monday-night football was the best for that! Damn, I could make $100.00 or more off just one table of drunks, and I had a whole section of tables filled with drunks! Most servers don't want the tipping to go away in the US and just get a living wage because they can make a lot more in one night working at a bar or restaurant than an office worker makes in a week or 2. That said, the cruise ship service people don't make that much off of the tips. It just brings their wages up to a living. They are not going home with huge rolls of cash at the end of the cruise as we used to from a single night serving drinks in a bar or serving food in a fancy restaurant.
Even on our first cruise back in 1977, we left that much in an envelope to be shared by all. Here is the deal, if the cruise lines start paying everyone so no tips exist you all are going to be paying a hell of a lot more than $18 a day more for your cruises. So if I were to go out to eat every day for 7 days and tip $10 for breakfast and lunch each and $20 for dinner that would be $280 for just the waiters serving me my meals. Then another $140 for $20 a day for the stewards who clean up after everyone's dirty bums would be $420 in tips, and then the bartenders which would probably be for most cruisers $20 - $40 a day or $140 - $280 in tips. I mean this is just what you would tip in the US if you went out and did all the things that you do during a day on a cruise. That $18 is nothing!
The way I look at is I prepay the tip knowing that each person is only getting a dollar or two, and then I make sure that those who go above and beyond are getting extra tips beyond that. That said, I don't drink alcohol, I don't like coffee, I don't drink sodas, I like tea, but generally won't think to order. I am someone who downs the water. I can afford to share the wealth with the crew since I am not wasting it on what I see as "stupid stuff". That is my opinion of course!