Personally, I think Mr. or Ms. aaa's parents take care of the tipping, and everything else, but that might be a bit presumptive since I find it hard to believe anyone educated in the UK can have such poor communication skills.
The old saying is, when in Rome, do as the Romans. Tipping is a fact of life on most cruise lines. Regardless of your customs at home, the custom on board ship is to tip those who serve you at a level commensurate with the level of service provided. Stiffing a cabin steward or dining room waiter because some barista thinks it's all right to place a jar by the cash register cannot be justified.