The larger cruise lines -- those owned by Carnival Corp. -- already have done away with the TITOs. In order to play their slots, you have to insert your cruise card, create a pin number and the machines are programed to either allow the player to use cash to load the machine, withdraw cash from your winnings or charge additional play to your shipboard account. When you finish play, your winnings are deposited to your card by selecting a keypad on the machine and picking the transaction you want to do. When you are ready to quite for the night, you can take your card to a special cashier, enter your pin and they will pay the balance off your card. That leads to more profits from their machines, less maintenance of equipment and gives the cruise line the advantage of possibly getting more money from an undisciplined player who might continue to withdraw money from their shipboard account. One reason not to play slots at sea is that no uniform gaming laws apply at sea and casinos can set their machines to whatever return they want.
Also, all the newer machines that are being added have the low wager buttons blocked so a .01-cent machine really costs .18-cents to play (9 lines X 2 per line equals .18-cents). The same applies to .25-cent slot machines. The rational for this betting structure is based on "if you don't like our rules, don't play." I can only speak for the ships under Carnival's umbrella -- not sure about Norwegian, Royal Caribbean, etc.
Thanks for everyone who responded to my original post.