Was on the Diamond Princess 5-15/22 so I can speak for that ship only. There was a laundry aboard with a $1.00 charge for washing and $1.00 for drying.
Room service is provided free of charge... Our steward was fabulous so we compensated him by slipping him some cash at the end of the cruise. Princess says you are supposed to pick up an envelope at the purser's desk for any tips you wish to give to the staff, and they will distribute accordingly. Didn't want to do that because I would think it wouldn't not make it to the steward.
Room service is no charge...but you are expected to tip. The money in the auto tip does not include room service delivery (since many people do not use room service).
Believe me, if you hand the money to the steward, he/she will turn it over. They don't want to chance losing their jobs. If you leave the auto-tip in place, the steward we get the extra cash back anyway.
I have read that the auto tip is divided between all the crew that gets tipped, and anything that you hand them in cash, they get to keep. That may have been on HAL though. I would think it would be the same on all the Carnival lines?