I understand your concern. It would be very imprudent for any operator to suggest withdrawing these tickets as while the revenue is low on an individual basis revenue quickly stacks up over days and weeks.
Certainly the loss would be quite noticeable. For instance it is not unusual for the onboard spend of passengers on the ferries to equal or surpass the revenue from their fare (i.e. meals/shopping/Plus lounge/ cabin et cetera...)
On an aside WHSmiths in Holyhead terminal shut some months ago and the replacement facility (same unit) #EatDrinkShop remains open till approximately 01.30 nightly - useful for passengers going both ways.