Don’t forget all ships, cruise, cargo, tanker etc, etc, leaving or entering Ports have to adhere to a schedule, if a ship misses its time slot it could be an hour or even longer before a new slot becomes available.

I know from living near the Port of Harwich and from watching sail aways, when a ship is delayed in leaving, they then have to wait until other scheduled incoming vessels have arrived before they can leave. The delay could cost the cruise lines thousands of £s in extra port fees.

I know this from conversations with our daughter, who works for a company in Harwich (not cruise related) which has regular visits of shipping tankers, any delay in turning the tankers around can be extremely expensive for the company.

Cruise company’s have an obligation to wait for passengers who may be delayed arriving back on board, due to delays in the ships own arranged excursions, but do not have the same obligation in regards to those who have chosen to disembark on their own. Although I am sure if the passengers contact the ship and they have a genuine reason for the delay (not just forgot the time) they would be considerate in their decision.